A decent tripod is:
1. Strong and sturdy. They are two different things. Strong enough to support the weight of your equipment. Sturdy in terms of the life you get from it. A good tripod can last a lifetime.
2. A good tripod is a stable platform not subject to outside forces that would cause vibration. Hard wood is best, but heavy and awkward and usually not used for those reasons. Good carbon fiber is both stable and expensive. Aluminum is stable but less expensive.
3. Minimum and maximum height should be what meets your needs with out extending a center column. Extending the center column decreases stability. The only real combat to this is money. A very good, which usually translates to high dollar, tripod will be pretty stable with the center column extended.
4. It must be something that you can easily put into use. If you don't use it because it is hard to set up, is time consuming to set up or is too much of a bother to take with you, then it's not much good no matter the cost.
A decent tripod for any prospective buyer comes down to what their needs are and what they are willing to pay. Read over this article by Throm Hogan.
Tripods and Ball Heads by Thom Hogan
You don't have to spend the kind of money Throm does to get a good tripod, but he makes some good points about getting what really suits your needs now, or working your way up to it at a higher cost.