There are three basic tripod heads to consider.
- Pistol Grip
- Ball Head
Ideally you want something that permits 360 degree rotation, forward/backward tilt, and left/right tilt for vertical shooting.
The two-handled Pan/Tilt models are generally less expensive, but are somewhat awkward, and have a limited range of motion.
Some photographers prefer the convenience of a pistol grip that allows the camera to be moved in any position by squeezing the grip.
Finally there is the option of a Ball Head. While these types of heads are the most expensive solution, they provide a smooth experience in which you can point the camera in any direction quickly and securely. You can also pan and swivel making it a very versatile tool.