Travel-focused tripods for instance, like those found in the Velbon Ultra and Gitzo Traveller ranges, offer a great combination of low weight and compact dimensions, making them a perfect partner when travelling. Others though like the 3 Legged Thing Steve can be monsters, offering an incredibly solid platform at an extended height from which to shoot with even the heaviest of kit and are more suited for studio use.
And the weight of your kit is an important consideration - work out the weight of the camera equipment you intend to use with it (your heaviest lens and camera combination is a good starting point), as most manufacturers will list a maximum load capacity that the tripod is designed to support.
Next, how high and low to you want to be able to shoot from? The maximum extendable height refers to the overall height the tripods stands at with the legs and centre column fully extended, while minimum-working height refers to how low you can shoot off the ground.