There isn't a birthday today without a camera (or two) and a video cam on hand.
However, there are a few simple steps you should take to make sure these devices function properly during the party and give you the best results.
First, BEFORE the party, make sure your camera is fully functional and that you've got spare batteries AND more than enough film or smart media cards.
You should also designate a family member or friend (who KNOW how to use the camera well) to be the photographer. It'll free you up to take care of more important things.If you're having a large party, get a few disposable cameras and ask some of the parents to take pictures for you also. It'll be fun for them and you'll get a few different perspectives.
Make sure you instruct the "designated" photographer to take pictures of important moments (like when the candles are blown out...) and also to try and get a shot of ALL the guests. These can be used for the thank you cards.
A great idea is to set up comical photo station around the entrance to the party and snap photos of each child as they arrive. We did this at our last Safari party and the thank you cards were hilarious.
Here's a WONDERFUL article written by and expert photographer to help you use your camera take the very coolest birthday party photos.