Widescreen Works Best
So many people make the mistake of holding their iPhone vertically when shooting Youtube videos. The widescreen horizontal format works much, much better on most hosting sites.
Use A Tripod
There's nothing worse than shaky videos so use a tripod whenever possible. You can pick up an iPhone tripod adapter for pennies so get that on your shopping list.
Avoid the iPhone Zoom Function
If you try and zoom in with your iPhone you don't get an optical zoom so don't do it. When you zoom in with your iPhone it's just a digital enlargement so that's going to create pixellation.
The camera in the iPhone these days is so good that you don't need professional lighting. Daylight works fine so make sure you take full advantage of the natural light and start recording.
Use The Exposure Lock
The automatic focus function means that the iPhone camera will keep shifting focus to follow your subject. That can spoil your video, so use the exposure lock to create a consistent and seamless recording.
Improve The Microphone Sound Quality
If you are looking to create a quality Youtube video or for any other purpose, then it's just as important to get the sound quality right as it is the image.
The in built microphone is fine for a quick video, but for anything else you are going to need to do some editing anyway, so it's a good idea to create a separate sound track using a second iPhone, close to your subject, or an alternative microphone.
A great tip is to clap before you start recording so you can synchronise the two sound tracks.
Shooting youtube videos with an iPhone means that you need never miss a recording opportunity. The quality is excellent and with a little bit of preparation you can create some awesome videos without ever needing expensive camera equipment.