random generators, or simply making it up completely. sometimes it can work to combine two names of already existing characters or just some random names/words/whatever. also sometimes I try to base the name on the type of personality the character has (though it doesn't always come out the right way, and I end up with an assassin with a kinda-cute name).
for some characters, mostly spirits etc. I use translators for the language of the culture to which the character belongs (for example a katana's spirit is named in japanese) and translate the words that have something to do with the character.
generally varies by character, though I often reuse names from my other stories and RP sites, too.