Need more info.

How big is the pot? How big is your stack, an your opponents?

If I'm in a dominating chip position I put pressure on with a bet. If there is a bet ahead of me I raise significantly if I get a read that the bet was a probe or continuation.

If the flush doesn't hit on 4th you are likely to get a free card to the river. In this regard you save a bet if you were planning to draw to it anyway.

With a shorter stack, check and see the card every time. Either that or push in like you are protecting from it maniac styleeee. :P