It depends on a few things such as the texture of the flop and your perceived table image. If the flop has a flush / straight draw and you're up against more than 1 or 2 players, you need to bet big to scare some of them away. However, if the flop comes rainbow you can slow play it. In addition, you need to ask yourself "what do they think of me?" If you normally throw out a bet after the flop, then do so here and let someone else take the lead betting.