What's the right bet size on the flop when you have top pair , top kicker and your opponent is on a flush draw ? Effective stack was about 50 bb. $1/2 NL
I raised in the co. position and the button calls. I bet $30 into a $40 pot on the flop with tptk. button calls. turn is a blank. I shove all in $60 into a $100 pot. button calls and hits his flush on the river. Should I have shoved on the flop ?

What sort of game are you playing in which your opponent shows you his cards? The answer is, the maximum bet size that he will call. You don't need to consider odds as such because for some reason you know exactly what he has so you won't put in any more money if he gets his flush...unless of course you boat up.

3/4 pot on the flop is fine.
60% of pot on the turn is also fine. Villain doesn't have the right odds to call. He sucked out. That's poker!

Looking back on the hand , my thought is that a 3\4 pot bet on the flop always gives your opponent the correct odds to call with a flush draw. Then I wasn't deep enough to force my opponent into a wrong decision on the turn.

3/4 is fine iMO.

With that stack and pot size you should definitely be planning to ship it asap with TPTK and your flop sizing is perfect imo because it sets up a reasonable shove on the turn. You got the maximum value possible out of that hand (in Sklansky bucks at least), can't be upset about that.

Shoving flop is not good because you want those draws to call -- $100 into a $40 pot is only ever getting called by the nuts, you're folding out tons of worse hands that are going to pay you off (and draws that are going to miss most of the time)

Actually your bet doesn't give him anywhere near correct odds to call on the flop, and he still makes a bad decision on the turn. In each case it is about 4-1 against him making his flush, and you aren't giving him nearly 4-1 pot odds with either bet. Don't confuse yourself with the rule of 2 and 4 and think that on the flop he has about a 1 in 3 chance of getting a flush. That is only if he sees the river, but your bet that he has to call is just to see one card. Since you followup with an all-in on the turn, you are giving him bad odds twice and he just got lucky. That doesn't mean you did anything wrong.

thanks for all the great replies. I will definitely continue using this forum to gain infinite knowledge on poker.