If you are holding two suited cards and are fortunate enough to flop a flush, you are going to want to raise your opponents.Ideally you will not be facing more than two other players after the flop, so you should take control of the betting by raising or re-raising. You may experience trouble in getting action back from players who fear your flush or have not improved their hands on the flop. By raising you will get calls or re-raises from players who do not give you credit for hitting a flush, and have hit on the flop, hands like over-pairs, TPTK, sets or players who are on draws.
You should not consider slowplaying a flush, as you want to be able to drive out hands that may improve against you on the next two cards. A player who hits a set will have outs to a full house, so your bets need to be big enough to give them the wrong odds to call your raise. You must also be wary of players who are on a flush draw. If you are not holding a nut flush, you are going to have to be careful that a player that is holding a card that gives him a draw to a higher flush on the turn, again you do not want to give them the correct odds, because a player holding a card like the Ah, on a flop of 6h-Jh- 9h, is going to call raises, but you need to more expensive for them to do so.
If you are originally raised and re-raised again, you could be up against another flush, or a player on a nut flush draw, it would be wise to call the raise and then check and call the hand down.