it depends on a few things i think.

firstly how youve played the hand, if youve played it in a way that youre obviously drawing as soon as the board completes that flush the other guy is gonna shut down - people greatly overestimate the implied odds of hitting a flush. this may not be the case if he has a a big pair in the hole, like aces, that people find hard to lay down or two pair again for the same reasons. However most of the time the other guy will have a pair and lay it down when the scare card comes up and hed put u on that draw.

so in this case on the turn it my not be that bad an idea to check and make a bet on the river instead. of course this isnt gonna encourage any more action in most cases as it just looks like youre slowplaying, so it depends on your table image (if its aggressive then probably not a good idea). if you complete your flush on the river you obviously have to bet.

another point is if you put him on a set and youve made your flush on the turn you should bet out a good sized amount because if the board pairs on the river youre gonna have to throw your hand away, so u need to take it down there.

if youve got a good draw it might be a good idea to build the pot before you make your hand, if the other guy is deep and also if you put him on a big hand. This way if your card does hit you may stack him (or double up). Of course this is only going to be profitable if he is deep and youre therefore risking some money to make a lot, if hes short or even medium stacked its probably not a good strategy as your gonna be risking chips with not that much to win.

with regard to straight draws, your implied odds of completing the straight are much higher than with a flush. people, at least at micro and lower limits, tend not to shut down with another scare card, unless its blindingly obvious. its not just gutshots etc that will get paid off (at lower limits) even open ended straight draws that complete are likely to get paid off. so bet.

If the chaser hits and knows he's not getting more money out of the pot, what's the difference between betting and checking? In this instance, a check is better.

If he bets out, you fold, he only takes the pot.

But say he checks and you just hit a set, or a straight with his flush. You never really know if someone has the flush or not, regardless of how the hand was played. But you just hit a monster that can only be beaten by the flush, but what if he had a three-flush to the nuts and a pair? He'd play it like a drawing hand.

You're saying you're not going to bet out a straight at a coordinated board even if only for 1/3 to 1/2 the pot? I would. He could be chasing a set, backdoor flush, and a gutshot. There's just no guarantee he hit his flush.

If he raises you, you're done with the hand. But he's picked up an extra bet.

Out of position, please bet when you hit your draws. If it's not a good spot to bet because you don't think you're getting paid off, you should've check-raised earlier and taken down the pot.