Common newbie mistakes for cinematography?
Common oversights of beginners in pre-production:

1) No script or plan of action. Even if you are doing something very abstract or experimental, have a plan of how things begin, develop and end. You can always change this as you proceed, but it's most important to have a baseline. This should include your budget of money and time for all concerned.

2) No research. If you are shooting a documentary or a narrative be sure to do all the fact checking or if this is fiction, make it plausible or not if you desire the comical.

3) No storyboard. The storyboard is a series of panels like a comic book that describes each scene and the action contained within. This is how the camera will set up for each shot. From the storyboard you can derive a shot list.

4) No idea of screen direction. Right from the storyboard you should have a good handle on the direction the action moves within the frame as well as taking into account how the camera may move to cover such action whether that is a pan, tilt, crane, handheld, etc. shot. The key here is continuity of movement from shot to shot. Learn about screen direction and cover the 180 degree rule as this also falls under continuity.

5) No production schedule. Most movies do no shoot each scene in the scripted sequence because you can save a lot of time and money by shooting by location, time of day, or other logistical considerations. I once worked as an Hollywood extra in "Indiana Jones and the Temple of Doom". The last shoot or wrap night as they called it was actually a sequence near the beginning of the film. Plan your shooting schedule to optimize each location as appropriate.

Common oversights of beginners in production:

1) Not locking down exposure, focus, and white balance.

2) Terrible lighting. Learn about shooting with existing light, and how to make it work with reflectors if need be. If you are shooting indoors, learn about basic 3 point lighting to start. The most important thing is to make sure your subject is lit well and defined.

3) Terrible sound recording. Learn the basics of sound recording, like setting the level so it does not exceed peak load and not changing the recording level while recording. Also, get creative with sound too, learn about Foley and explore ways to create your own effects.

4) Camera shake: it's one thing to shoot hand held but if you are trying for a steady tripod shot, make sure you don't touch the camera when its recording. For instance one of my cameras has a remote so I can start and stop it with out even getting near the camera. Also, if you are using a tripod be sure that it has enough weight to handle the wind. For hand held shots shoot wide angle as vibration is proportionately magnified by increasing focal length (zooming in).

5) Over zealous use of zooming. Learn to use the zoom feature when it is transparent and does not call attention to itself. For instance a more effective use of zooming in or out is done simultaneously with a pan or tilt (assuming you have a tripod with a fluid head) while following an action. A good example of this is how a sports cameramen will follow a play such as someone trying to steal 2nd base.

6) Learn to compose a shot. Use the law of thirds in framing a subject, and when to make exceptions. I highly recommend art history 101 for beginners to learn about composition. Study the greats from Leonardo da Vinci to Pablo Picasso to understand how to frame your subject and study film history 101 to learn how great directors worked with framing in motion, e.g., Orson Welles' work in "Citizen Kane". Others: Billy Wilder, Alfred Hitchcock, Akira Kurosawa to name a few.

7) Didn't get enough takes to cover the action. Make sure that you have enough good takes of each shot on the shot list. Be sure to allow some flexibility with adding long shots, medium shots, and close ups all with different angles to optimize the light and action. Shooting more is better than less from an editing point of view. Editors love to have tons of stuff to choose from as long as these extra shots highlight the intent and the director is behind it.

Common oversights of beginners in post-production:

1) Wrong format. Be sure that your camera files are compatible with your video and music/sound editing suite.

2) Too much time on one clip. Unless you are using a steady moving crane shot don't expect to keep anyone's attention if your shots are too long, and don't have any sense of movement or action. Having a wide variety of long, medium, and close up shots with varying angles to choose from that cut swiftly on action and appear transparent will be more engaging to your audience.

3) Jump cuts: this is all about continuity, learn when and when not to use a jump cut.
One acceptable form of the jump cut is the 'magic cut' such as some one suddenly appears in the frame like in Star Trek when they beam up. A bad jump cut is when something that may have been in the previous scene is misplaced in the following shot or the reverse is true too. There are a zillion examples of jump cuts. One famous one is Dustin Hoffman driving the wrong way on the SF Bay Bridge in "The Graduate".

4) Over use of effects. There is a huge temptation to over use an effect you may find interesting, even experienced cinematographers can easily over use something new to them and unfortunately your audience finds this boring and distracting. The golden rule is to use effects sparingly but appropriately when used. The best way to learn this is to see how this effect has been successfully used before by professionals in great movies.

5) Non-original music. Too many beginners use popular music for their productions. Even if it appears to fit, we've heard it already. Does "Also sprach Zarathustra" have to always play for a sun rise or moon rise? The question you should ask yourself is, how many buddies of mine play music, how many are good and want to work on it with me? Got a friend that can compose? Original music makes any production refreshing and takes your film from the ordinary to the unique as long as you make the music interesting and supports the film action.

6) Pay attention to the basic rules but don't be afraid to take some risks. My number one rule is that if I break one I better have a darn good reason and it really has to work within the context of the film I am working on.