If he has high pocket pair vs your set, he has 2 outs to beat you. Plus 9 outs for the flush draw (or 8 if you're holding one of his outs) with two cards left, that means he has a 23% chance of getting his outs on each street. (45% by the river, but you're going to have two rounds of betting by then so we look at what we're going to make him pay for each street because we can back out if he hits his outs.)
Basically you have to make him pay more than his pot odds
to see the next card. If he is paying more than he should to play, then you profit.
I'd say bet 3/4 pot to full pot. We would prefer him to fold before he hits his outs, but he doesn't hit his outs, you're going to pull in a nice pot. If you bet half pot, then he is getting his odds to play. If there's 20 in the pot, bet 15 to 20. We don't want to bet more than that because we don't want to pay more than we have to if we're wrong about what he has
I guess long answer short is: Just don't give him the right pot odds
and what he does from there is up to him, either way is profitable for you.