I'm along the lines of Tarot, above. I prefer to make some decisions ahead of time about what sorts of things might be encountered in a given area...what lives there, be it wild animals, tribes of orcs, a motorcycle gang, or what-have-you. (Actually, the what-have-yous are pretty dangerous, so I try not to use them much. ) Then, I can always roll encounter checks and pull out something handy if one comes up positive. Doing a complete random encounter on the fly...figuring out what, how many, hit points, and so on...is an incredible drag on any kind of momentum in the session.
I'm not stupid, I'm not expendable, and I'm not going! (But I'll happily be the GM...)