First, and most importantly, know what genres of photography you enjoy the most and if that genre requires a tripod. Then, buy the largest, highest quality tripod you're willing to carry that fits in your budget. Specifically in that order; do not put budget ahead of any other aspect of the tripod. If you go too cheap, you may very well end up with a tripod that meets none of your needs when you're forced to replace it due to instability or fragility. The adage, "buy cheap, buy twice (or more)" applies here.
I finally have my dream 3 tripod setup. Gitzo Systematic GT3543LS+GH3382QD, Mountaineer GT1542+GH1382QD, and Traveler GT1555T+GH1382TQD. Next up is the Gitzo GM2542 Monopod and Mini Traveler Tripod. I plan to give all of them a thorough shakedown in Long Beach, WA in a couple of weeks and then in the North Cascades the week after. That is all.