user8486: 
“Awesome! Those unknown materials are waiting for me! I'll have to get my gadgets out then.” — Nitori Kawashiro.

Step 1: Read the community wiki below.
Step 2: Share your tools and know-hows that trump all the others in at least one instance of answering an identification-request question.
Step 3: ???
Step 4: PROFIT!!!!

user274: Videos
Capture a screenshot of the video and do a reverse image search with that, or enclose subtitles, if any, in quotes and do a text search using Google.

Tip: If the video is from YouTube, Vimeo, etc, read the title, description and comments carefully! Chances are, the answer is already written there.


user274: Characters
When looking for a specific anime character, there are search engines that are designed to help with exactly that. Anime Characters Database, Anime Planet and aniSearch are three such sites. You can input details such as physical attributes (hair color, eye color, etc.) or character attributes (phobias, voice characteristics, school year, etc.).

Tip: If your character doesn't show up in the first 100 results, try removing an attribute that you might not be sure of. For example, in the exercise below, the character's eyes appear brownish, but are actually red.



Exercise: Identify the character on the television in this question by searching for a black- and shoulder-length-haired adult male on Anime Characters Database.


user274: Music
The major players in the music identification category are: Shazam, SoundHound and TrackID. Unfortunately, when it comes to anime songs, all three apps have a rather abysmal identification rate that renders them near useless. For this niche purpose, I use Xiami.

Tip: Try different song segments for identification and remember to check for false positives!



Exercise: Identify the piece of music requested by this question. I recommend using Shazam or TrackID for this exercise, as SoundHound identified a recording that is not the anime version.


user274: Images
ImgOps is an extremely useful meta-tool for image operations. It incorporates the following reverse/similar search services: Google, Bing, TinEye, Reddit, Yandex and Baidu. Bing, TinEye and Reddit all perform poorly in my experiences. Yandex looks promising, but I haven't tested it enough to be able to judge its strengths and weaknesses. This leaves us with Google and Baidu. For a specialized treatment on how to reverse image search using Google, please refer to this post.
Baidu's specialty lies in identifying the name of the series from anime screenshots and manga pages, and sometimes even surpasses that of Google.[case 1][case 2] Its similar images feature is also often quite accurate. It's better to pass along the unencrypted image URL (no https in the prefix) as you might encounter this error page otherwise:

That page also shows up if you uploaded the image from local to ImgOps and followed Baidu's link from there. No worries, just click on the blue button to upload from local, or drag the image to or paste the image URL in the adjacent white box. It may be a bit tough to use Baidu Shitu (Shi-tu, not Shit-u) if you don't understand Chinese. Nevertheless, Baidu is a serious contender to Google in the reverse image search department.
I also note other resources linked to by ImgOps that might come in handy at times: anime (iqdb), anime+ (saucenao) and gif-explode. The first two are useful for finding anime wallpapers and artworks, while the last one can be used to break an animated GIF into its individual frames so you could cherry-pick the frames that will return a hit from reverse image search.

Tip: If reverse image search didn't turn in anything useful at first, wait a couple of weeks/months and try again. The (full) image could have been indexed by the search engines during this period, so you might get lucky like me and find it in your subsequent trials.



Exercise: Crop the image from this question and reverse image search with Baidu. You should get something like this:

Although the romaji is given in this case (Chou Majin Eiyuuden Wataru), you should still know how to proceed from here if it weren't given. Copy the Chinese characters enclosed in either of the red boxes added by me, and do a Google search on those characters together with the word "English". It is not clear to me if one would be able to get the name of the other series (Madou King Granzort) without knowledge of Chinese: let's leave that as a challenge.

For specific techniques on reverse image searching, see this meta post.

user8486: Text
Google Search is your obvious choice. You should also utilize punctuation, symbols and operators in your searches to get the most out of what Google Search has to offer. I find myself most frequently using the symbols " and, to a lesser extent, _ and -.

Note: Google will customize search results according to a number of different factors. This means that different users will see different results for the same search terms. These factors include, but are not limited to:

Country and location
Language
Device
Browsing history
SafeSearch filter setting

It is impossible to entirely remove the variance in search results because some of the factors are totally outside users' control, e.g. algorithm testing and update lag across data centers.



Tip: Do your search in another language if you're not getting satisfactory results.



Exercise: Try to find the answer to this question by typing comic single for 16 years into Google's search box. Now, try comic "single for 16 years" -site:stackexchange.com. Which web search query was easier for you to find the answer?


8486: <p><img src="https://i.stack.imgur.com/p7Zqj.jpg" alt="Obligatory Touhou"></p>

<p><em>“Awesome! Those unknown materials are waiting for me! I'll have to get my gadgets out then.”</em> — Nitori Kawashiro.</p>

<hr>

<p><strong>Step 1:</strong> Read the community wiki below.</p>

<p><strong>Step 2:</strong> Share your tools and know-hows that trump all the others in at least one instance of answering an <a href="https://anime.stackexchange.com/questions/tagged/identification-request" class="post-tag" title="show questions tagged &#39;identification-request&#39;" rel="tag">identification-request</a> question.</p>

<p><strong>Step 3:</strong> ???</p>

<p><strong>Step 4:</strong> PROFIT!!!!</p>
 274: <h2>Videos</h2>

<p>Capture a screenshot of the video and do a reverse image search with that, or enclose subtitles, if any, in quotes and do a text search using Google.</p>

<blockquote>
  <p><strong>Tip:</strong> If the video is from YouTube, Vimeo, etc, read the title, description and comments carefully! Chances are, the answer is already written there.</p>
</blockquote>
 274: <h2>Characters</h2>

<p>When looking for a specific anime character, there are search engines that are designed to help with exactly that. <a href="https://www.animecharactersdatabase.com/search.php" rel="nofollow noreferrer">Anime Characters Database</a>, <a href="http://www.anime-planet.com/characters/" rel="nofollow noreferrer">Anime Planet</a> and <a href="http://www.anisearch.com/character" rel="nofollow noreferrer">aniSearch</a> are three such sites. You can input details such as physical attributes (hair color, eye color, etc.) or character attributes (phobias, voice characteristics, school year, etc.).</p>

<blockquote>
  <p><strong>Tip:</strong> If your character doesn't show up in the first 100 results, try removing an attribute that you might not be sure of. For example, in the exercise below, the character's eyes appear brownish, but are actually red.</p>
</blockquote>

<p></p>

<blockquote>
  <p><strong>Exercise:</strong> Identify the character on the television in <a href="https://anime.stackexchange.com/q/4767">this question</a> by searching for a <em>black- and shoulder-length-haired adult male</em> on Anime Characters Database.</p>
</blockquote>
 274: <h2>Music</h2>

<p>The major players in the music identification category are: <a href="https://www.shazam.com/apps" rel="nofollow noreferrer">Shazam</a>, <a href="http://www.soundhound.com/soundhound" rel="nofollow noreferrer">SoundHound</a> and <a href="http://www.sonymobile.com/global-en/apps-services/track-id/" rel="nofollow noreferrer">TrackID</a>. Unfortunately, when it comes to anime songs, all three apps have a rather abysmal identification rate that renders them near useless. For this niche purpose, I use <a href="http://www.xiami.com/apps/mobile" rel="nofollow noreferrer">Xiami</a>.</p>

<blockquote>
  <p><strong>Tip:</strong> Try different song segments for identification and remember to check for false positives!</p>
</blockquote>

<p></p>

<blockquote>
  <p><strong>Exercise:</strong> Identify the piece of music requested by <a href="https://anime.stackexchange.com/q/14380">this question</a>. I recommend using Shazam or TrackID for this exercise, as SoundHound identified a recording that is not the anime version.</p>
</blockquote>
 274: <h2>Images</h2>

<p><a href="http://imgops.com/" rel="nofollow noreferrer">ImgOps</a> is an extremely useful meta-tool for image operations. It incorporates the following reverse/similar search services: Google, Bing, TinEye, Reddit, Yandex and Baidu. Bing, TinEye and Reddit all perform poorly in my experiences. Yandex looks promising, but I haven't tested it enough to be able to judge its strengths and weaknesses. This leaves us with Google and Baidu. For a specialized treatment on how to reverse image search using Google, please refer to <a href="https://anime.meta.stackexchange.com/questions/793/how-can-i-identify-an-anime-using-reverse-image-search">this post</a>.</p>

<p>Baidu's specialty lies in identifying the name of the series from anime screenshots and manga pages, and sometimes even surpasses that of Google.<sup><a href="https://anime.stackexchange.com/questions/18647/which-anime-is-this-kissing-scene-from">[case 1]</a><a href="https://anime.stackexchange.com/questions/20324/anime-with-a-boy-wearing-a-sun-shaped-crown">[case 2]</a></sup> Its similar images feature is also often quite accurate. It's better to pass along the unencrypted image URL (no <code>https</code> in the prefix) as you might encounter this error page otherwise:</p>

<p><img src="https://i.stack.imgur.com/ik5lq.png" alt="Baidu Shitu Beta is telling you to upload image from local"></p>

<p>That page also shows up if you uploaded the image from local to ImgOps and followed Baidu's link from there. No worries, just click on the blue button to upload from local, or drag the image to or paste the image URL in the adjacent white box. It may be a bit tough to use Baidu Shitu (Shi-tu, not Shit-u) if you don't understand Chinese. Nevertheless, Baidu is a serious contender to Google in the reverse image search department.</p>

<p>I also note other resources linked to by ImgOps that might come in handy at times: anime (iqdb), anime+ (saucenao) and gif-explode. The first two are useful for finding anime wallpapers and artworks, while the last one can be used to break an animated GIF into its individual frames so you could cherry-pick the frames that will return a hit from reverse image search.</p>

<blockquote>
  <p><strong>Tip:</strong> If reverse image search didn't turn in anything useful at first, wait a couple of weeks/months and try again. The (full) image could have been indexed by the search engines during this period, so you <a href="https://anime.stackexchange.com/questions/15222/anyone-know-what-series-this-image-belongs-to/16938#16938">might get lucky like me</a> and find it in your subsequent trials.</p>
</blockquote>

<p></p>

<blockquote>
  <p><strong>Exercise:</strong> Crop the image from <a href="https://anime.stackexchange.com/questions/20324/anime-with-a-boy-wearing-a-sun-shaped-crown">this question</a> and reverse image search with Baidu. You should get something like this:</p>
  
  <p><img src="https://i.stack.imgur.com/MNY8p.png" alt="What do I do if Baidu Shitu&#39;s suggestions are in Chinese?"></p>
  
  <p>Although the romaji is given in this case (Chou Majin Eiyuuden Wataru), you should still know how to proceed from here if it weren't given. Copy the Chinese characters enclosed in either of the red boxes added by me, and do a Google search on those characters together with the word "English". It is not clear to me if one would be able to get the name of the other series (Madou King Granzort) without knowledge of Chinese: let's leave that as a challenge.</p>
</blockquote>

<h3><a href="https://anime.meta.stackexchange.com/q/793/274"><strong>For specific techniques on reverse image searching, see <em>this meta post</em>.</strong></a></h3>
 8486: <h2>Text</h2>

<p><a href="https://www.google.com/" rel="nofollow noreferrer">Google Search</a> is your obvious choice. You should also utilize <a href="https://support.google.com/websearch/answer/2466433" rel="nofollow noreferrer">punctuation, symbols and operators</a> in your searches to get the most out of what Google Search has to offer. I find myself most frequently using the symbols <code>"</code> and, to a lesser extent, <code>_</code> and <code>-</code>.</p>

<blockquote>
  <p><strong>Note:</strong> Google will customize search results according to a number of different factors. This means that different users will see different results for the same search terms. These factors include, but are not limited to:</p>
  
  <ul>
  <li>Country and location</li>
  <li>Language</li>
  <li>Device</li>
  <li>Browsing history</li>
  <li>SafeSearch filter setting</li>
  </ul>
  
  <p>It is impossible to entirely remove the variance in search results because some of the factors are totally outside users' control, e.g. algorithm testing and update lag across data centers.</p>
</blockquote>

<p></p>

<blockquote>
  <p><strong>Tip:</strong> Do your search in another language if you're not getting satisfactory results.</p>
</blockquote>

<p></p>

<blockquote>
  <p><strong>Exercise:</strong> Try to find the answer to <a href="https://anime.stackexchange.com/questions/19597/looking-for-anime-shown-as-a-comic-strip">this question</a> by typing <code>comic single for 16 years</code> into Google's search box. Now, try <code>comic "single for 16 years" -site:stackexchange.com</code>. Which web search query was easier for you to find the answer?</p>
</blockquote>
