Well, it depends on which type of mic you're going to use. Poparad's recommendation works well with lavalier type microphones, but if you're using another type of micrphone it won't work.
Dynamic micrphones are the easiest to work, but they don't get much detail. They're less sensitive, which is an advantage in case of loud sound sources or noisy environments.
Condenser microphones, on the other hand, are usually very sensitive, so they will pick up the sound (and ambient noise) better. Most of them require a voltage to work, though (usually supported by the preamp phantom power, batteries or an external transformer).
Condenser and dynamics use XLR connectors. Nowadays you can get fairly cheap mirophones with decent quality, and a preamp. Look at the behringer and studio projects microphones, and basically any preamp with phantom power on the +-100 bucks range (they will mostly sound the same).