Your suited connectors have hit the flop, well kinda. You are on a draw, lets say a flush draw, and the player ahead of you bets. Assuming the bettor is the only other player in the hand, I say you raise. Here's why.
Senario one: The bettor is bluffing you off the hand. A raise from you, I'm thinking a raise about the size of the pot, will make him fold. Period. You win the hand.
Senario two: The bettor hit the flop, probably a pair or two pair. He will either fold his hand thinking your hand is stronger, or he will call. The advantage with the call is that he probably won't bet the turn knowing your aggression with this hand, whether he improves or not. If your flush card doesn't hit the turn, you may want to not invest anymore to the pot until you see the river, which you probably will for free. After seeing both the turn and river there is almost a 50% you have found the flush. If you have, take down the pot, it's yours. If not, and your opponent has checked both the turn and river, there is a good chance you can buy it anyway.
The problems that can arise are few and unlikely, but you should always be aware of the unlikely. First, you may catch the flush on the turn and not bet your opponent out of the hand. If the river is also of the same suit and you don't hold the nut flush, be careful that your flush hasn't been outdone. Second, if there is a pair on the table, be aware that your opponent could hold a full house. Barring those unfortunate events, feel confident with your flush.