Little by little. Say, I decide $2000 is my max, and I bid that. You only see my current high bid at, say, $300, so you bid $325 and instantly my high bid is $350. You go to $450 and instantly I've bid $475. Maybe you're intimidated, but more likely I've just got your back up by now, which is not my intention at all! I'm not interested in a pissing match, I'm just trying to buy a bike. Anyway, I've seen it many times: the "you" guy, little by little, ups his bid until he wins, not because he wants to spend that much, but because he doesn't want the other guy (=me) to win. So he wins the bike at $2100 and I don't. Fine! But I'd prefer to win it myself for far less.
^I agree with this and feel the same way.