You can shoot some awfully good video on your iPhone. These same principles will work on all smart phones.

 

First off  ... Launch the Camera and make sure you're in Video Mode.

 

Go to Settings ... Launch the settings app, Tap Photos and Camera, Tap on Record Video, Tap on preference. And choose your mode. I use 1080 at 30 fps

 

Next make sure you shoot in landscape mode. Most Computers, I Pads, Smart Phones, TV etc. are now widescreen or 16x9. Shooting landscape will make the video appear much better.
 

Now, center the subject and let the Camera auto focus and White Balance and then put your index finger on the screen to lock in focus and white Balance ... this will lock the exposure. 

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If you don't, image will try to keep up with movement and the focus and white balance will shift and flicker

 

Heres a few more hints. Don't used digital zoom on the camera or the pixels will get bigger and look fuzzy. Always put lighting in front of you and not behind or you will look like a silhouette. Use lots of light!