OK, let me tell you the biggest mistake people make when buying a tripod--they look for the least expensive option. I'm not saying you should go blow $1,000. I'm saying you can easily get a tripod that is $35, looks nice, and it's crap. You see, all tripods are compromises--you can't get one that is great at everything and also inexpensive. If you get one that is great for travel, it's not going to be as solid as one that has fewer leg segments and is heavier.
First and foremost, your tripod needs to be stable with your camera. Depending upon what you're shooting that could mean: stable on uneven, rocky ground, stable so if you bump in to it when in a studio you don't knock your camera over, stable enough to hold a body with a 600mm zoom for the wildlife you're shooting, or stable enough to handle a 2 minute exposure when you shoot astro photography. I'm not saying it needs to be all of those things. Only that looking at it in the store and extending the legs and it doesn't blow over doesn't mean it's "stable enough." Definitely go to a store and try out some tripods first (even if you order something online). Look at how much weight it can hold. Set it up and then try wiggling it.
Second, think of how you'll shoot with it. Are you looking to take long hikes with it? Then a composite model (which will save weight but usually be more expensive) is the way to go. Do you expect to fly with it a lot (so it needs to fit in carry-on luggage)? Then a tripod that folds down into about 14 inches is important. Are you going to use it for video? Then one that tracks/pans well is important. If you shoot wildlife then a tripod that can handle a gimbal is important. If you're shooting macro photography, product photography, or food photography, then a center column that can go upside or tilt horizontally is important. So you see, a tripod that is perfect for me might be mediocre or poor choice for you.
Third, a couple of things to consider. A lot of beginners will extend the legs and then raise the center column. That will substantially reduce stability on most tripods. Look at the tripod with the center column not extended. That height may give you a sore neck from having to bend over. Also, I shoot a lot of stuff in the dark--I put a strip of florescent tape on the legs so I don't bump in to the tripod in the dark. If you shoot in rough terrain, you might like a tripod that allows you to put spikes on the bottom. Also, the more segments to each leg (2 vs. 3 or 4), the less stable each tripod leg is likely to be.
As for brands, I've got a Manfrotto that I love and a Benro that I'm pretty happy with. They serve different purposes--one for studio/long exposures (it's rock solid). The other is a travel tripod that I can put in my carry-on luggage. I also have a Platypod (which is great for using a chair or a table or the top of a car as a tripod/stabilizer). I also have a Gorillapod (which I've wrapped around a small tree trunk or a fence rail). I also have a Monopod (which I use for sports photography--primarily soccer and football). As you see, different models for different needs.
Don't be intimidated by all this. The key lessons are: go to a store and play with some tripods to start to get a sense of the limitations of each feature. And think about how you'll use it (and let that drive what you look for). Remember, all tripods are compromises. And if you get a really cheap one, all it's good for is to use to beat off a potential mugger.