I know that this q is about the post flop play but just want to add that pre flop you should never sizing your bets according to your starting hand, that could be really good tell and perceptive opponent will fast take advantage of that play. So keep your pre flop bet same size for every hand, what you might do, according to Phil Gordon, is that you can bet bigger from early position and bet smaller from late position, but still it should be unrelated to the strength of your starting hand.
Now post flop, following the same logic your bet should be same or close sized whatever hand you flop and imho it should never be smaller that half of the pot size, somewhere between 2/3 and 3/4 of the pot is good thing, now it you have a note or realize that someone is a calling station you could increase your pot bet to the max that he will call if he keep calling every next hand you bet slightly more (important note, you do that only with strong hands, and if you are facing a calling station you should never try to bluf him) you should take as much money as you can and you'll do that by sizing your bet to the max that he will call, don worry if he calls your bet with draws, smart sized bet will make you money long term even if he hits his draw every now or then but even when he does he was playing against the odds and he still losing. Other thing when you flop a set or straight, you should bet more if there is a draw to a better hand then your (straight draw to your set or flush draw to your straight). Then again, there is few different scenarios of flopping a straight, top straight or bottom straight, now you see that bottom one can be easily dominated, according to Phil Gordon, it is ok to bet bigger on flop and take it right there because you can easily be dominated on later streets...
Another thing it is better to take initiative with made hand and call with draws if you have good odds to call, that only exclude monster draws like the one we talked in previous tread, but wit oesd and fd it is better to keep it smaller until you hit, with made hand like set, tptk, 2 pairs it is better to take initiative and bet accordingly to the flop and info on your opponents as we already said
Now to make this shorter if you wanna simplify things for freerols and low buyin tourneys bet between 2/3 of the pot and pot sized bet is OK IMHO
Hope this hepls