You need the hooka (or narghile), plus a small number of other things: shisha tobacco (basically tobacco mixed with molasses and aromatic additives), charcoal to heat the tobacco (you can buy special charcoal blocks for shisha), tin foil to secure the tobacco in the bowl, and a very-very good lighter to light the charcoal.
Generally, people are quite eager to show you how to use it when you buy one. And never confuse a hooka with a bong, mate - you are safe, really. Smoking any drugs from a hooka is enormously impractical (with the possible exception of opium), since most of the fine, fine high just burns away under the charcoal.
Final piece of advice: always keep it clean. The taste of the tobacco can really eat itself into the pipes and tank, and I assume you don't want to smoke the same flavour all your life.
Here is a handy picture from Wikipedia: http://en.wikipedia.org/wiki/File:Hookah-lookthrough.svg
Personal experience, Wikipedia