First thing you want to look at when flopping a
set is how coordinated the
flop board is. The problem with slow playing a
set past the
flop on coordinated boards is that your opponent puts you on the board (thinks you have a
flush or
straight). Sometimes they even have a
flush or
straight themself. It's often better to play it quickly, since any opponent you want paying you off has
top pair or better, and is not drawing. You
don't want the guy who is drawing in the hand with you (unless he vastly overpays), because practically speaking, your
set has a lot of
reverse implied odds. It's very hard to release.
The reason I say this is because the
turn 9 not only gave you a
full house (yah!), but also decreased your
implied odds (oh shit!). That is to say your opponent may think it's reasonable you hung around with a 9 on that
flop, and then caught
trips. This of course was just bad luck. The
flop was very favorable for a
slow play, and you were right to do so. You have to think on your feet however. When the second 9 comes you can't decide to come alive on it. Your opponent will put you on it, since the
flop action would suggest it's reasonable you hung around with
second pair. Instead it's better in this
case to continue slowplaying until the
river with such a strong hand.