How do customize the HTML output around a specific field using field.tpl I in the middle of creating a content type with multiple fields. All the fields need to have all the extra markup removed, except for a specific 3 and I would like these to actually be wrapped in &lt;h3&gt; tags.

I've copied the field.tpl file into my theme and renamed to be used just for this specific content type, which is working fine with this code:

  &lt;?php if (!$label_hidden): ?&gt;
  &lt;div class="field-label"&lt;?php print $title_attributes; ?&gt;&gt;&lt;?php print $label ?&gt; &lt;/div&gt;
  &lt;?php endif; ?&gt;

  &lt;?php foreach ($items as $delta =&gt; $item): ?&gt;
  &lt;?php print render($item); ?&gt;    &lt;?php endforeach; ?&gt;


My trouble is that I have no idea the syntax I need to target a specific field. So I'm im guessing once I figure out how to target the specific field, I can just use:

  &lt;?php foreach (something here to find the right field): ?&gt;
  &lt;h2&gt;&lt;?php print render($item); ?&gt;&lt;/h2    &lt;?php endforeach; ?&gt;


What would that be if my field name was field_sizing_title?

I found the Field Wrappers Module, but it seem like overkill and I really like to learn more about how to work with the field.tpl file
You need identify the field machine name. For example if you have a field called Name and have a machine name field_name the field tpl name should be field--field-name.tpl.php. 

See this thread as well as it provides a comprehensive guide on how to override field template using hook_theme and preprocess function. 

One of the most handy helper I used is $conf['theme_debug'] = TRUE; in settings.php. It will show a template suggestion in HTML source.