There's no easy answer to this. I tend to be more aggressive and I will raise from any position at most tables with KJ or better. The size of the raise varies considerably though. I don't have a standard raise for all so-called "raising hands." I will raise bigger with high pairs to try to take the pot down immediately, or at least limit the competition to one player. With more vulnerable hands like KJ, KQ, AJ, AQ, and AK I usually raise enough to weed out weak hands (min. 2X BB)... the raise gets bigger in late position. For example with a .50 BB I might raise to $1.50 from early position, but $2.00 or $2.50 in late position, with the same hand (depending on its strength - wouldn't over-raise like that with KJ from any seat). If I get re-raised, I might just muck my hand. A lot of people are scared to play borderline stuff like KJ and especially scared to raise with it from early position, but if you're confident in your post-flop play, and you don't mind folding to a re-raise pre-flop, you can do just fine.

But "it all depends." Depends on the table, if anyone else there is very aggressive, etc. You don't want to get into raise wars with someone else who raises any decent hand and is always trying to steal your bets.