How Do People Find The Cheats For Video And Computer Games?

When I play the Sims 2 on the computer I sometimes look up cheats for it. And there are websites with a bunch of cheats that someone posted. How do people find all those cheats?

Is It Possible To Use Computer Cheats With A Ps3 If You Use A Keyboard?

Every time i want to get a game, i keep wanting to get the ps3 version, but the computer versions have all of the cheats. If i hook up a keyboard to my ps3, can i access the cheat input thing and use the cheats. For example, for fallout 3 cheats?