Taxis are plentiful in the Downtown area, but elsewhere they're scarce and hailing one can be a very trying experience. So it's always best to phone for one. Cab companies include:
Taxis Fiesta tel: (713) 225 2666
Square Deal Cab Company tel: (713) 659 7236
Yellow Cab Company tel: (713) 236 1111
The usual tip is about 10% of the journey fare.