I play a lot of NL hold'em and one of the most common bad plays I see people make is calling all in after the flop with a 4-flush. Of course this is sometimes the right play, but more often than not, the bettor is getting insufficient odds to committ all of his chips to the flush draw. First off, I think you need to have the nut-flush draw. This is especially true in multiway pots where you could lose to a bigger flush draw. Weak players are especially succeptible to this mistake as they have a tendencey of overvaluing any two suited cards. Second, you would like to have overcards so that you also have the possibility of winning by pairing up. Even still, you should ussually fold this hand heads up as the odds are against you. If you happen to be up against a set or two pair, you're in even worse shape. That said, if you are getting 3-1 or better on your money it is probably correct to call. I just think think its a dumb play.

I mostly play limit hold-em, which in most cases it is correct to call with your flush draw, but in no limit it is a different story. Calling an all-in on a flush draw is almost never correct. However, moving all-in with your flush draw can be a very good move, especially with two overs.

Yeah, it's all fine as long as you have the odds and can take the variance. But, usually the odds aren't there unless 1 of the players is shortstacked, and if one could sustain the variance, they'd play for the max buy-in to insure that they could win the most on their hands.

If you're not getting 3-1 or better on the call, don't do it. There's no implied odds, no fold chances, your opponent has redraws to a FH most likely if they're doing the pushing. You hit the nail on the head, it's a sucker play a great deal of the time.