Pixiq

One thing that truly is different with video compared to shooting photos is sound. Audio can make a huge difference. Good audio can actually make your video look better, while bad audio can make video look worse. That is simply based on how we perceive things we are seeing that are shot as videos or even movies. Hollywood "sells" you on a lot of action shots because of the sound, not necessarily from the shots alone (try watching without the sound!).

Good audio does not have to be hard, however, getting good audio from a microphone built into a DSLR can be a challenge. Here are three quick tips:

1. Get close to the sound. Microphones do best when they are close.

2. Be aware of the sound all around you. Your lens only allows the camera to see what the lens sees. However, the microphone hears everything all around you, including the rustling of your nylon jacket (a bonus tip -- avoid noisy clothing!).

3. Add a shotgun mic to your hotshoe. These little microphones plug into the mic jack on your camera (though some manufacturers foolishly have not included this) and gain a much higher quality of sound than what your camera mic can do. They are not expensive and focus the sound capture somewhat so you hear less of noises off to the sides. I use a Sennheiser MKE400 and like it very much. 

Here is also a link to a video I did about audio for DSLRs -- http://www.youtube.com/watch?v=Z15ksroGMd0.