We dedicated several minutes to choosing a tripod in the video course we're helping to produce through
http://www.WeddingVideoDoneRight.com. There is as much to consider here as when you're deciding on a camera and it is no less important!
Check around the web and all the advice is to buy a light, lightweight tripod. But think a moment - what is the purpose of a tripod? Support, right? When you're doing a pan or tilt, you don't want a leg leaving the floor. There are aspects as to how the tripod opens and collapses that are important, whether the legs are independant or not and whether a ball leveller would be helpful. I could go on. And then, you have the subject of heads.
If you stay in the business, I'll wager that you'll eventually spend more money on a tripod than you spent on your first "professional" camcorder! But for most people, that will be two or three tripods down the road.
Rather than bore other members by repeating my detailed discussions on tripods and heads, please use the search feature of these forums and you'll find this has been rather heavily discussed. But don't let me discourage anyone who cares to weigh in here...