I agree with staresy.

Bet when it comes to you. If your opponent thinks you already have the flush there's a chance he's either made it too or is on a draw. Either way, he will be drawing dead if you made the nuts providing nothing else comes out that can help him.

Even if he doesnt think that, let him think that you're on a draw. A smart player will know the outstanding odds of making a flush on the next card and would be very careful.

Of course, take your own liberty to change these recommendations based on the table, player tendancies, and limits.