Need a line - flopped set (first post)

OK, so I suck and need to get better, so I'm posting hands I botched. This one certainly qualifies.

First the hand, then my thought process. No real read on villain, he had only shown down one hand, an AK that was beaten by a flush. However, he seems solid. But, this is a $5.50, so it's a fair assumption that everyone (myself included) is a donk.

PokerStars No-Limit Hold'em Tourney, Big Blind is t30 (7 handed) converter (http://www.selachian.com/tools/bisonconverter/hhconverter.cgi)

CO (t1375)
Button (t635)
SB (t2335)
BB (t2495)
Hero (t1285)
MP1 (t1910)
MP2 (t3465)

Preflop: Hero is UTG with 4/images/graemlins/spade.gif, 4/images/graemlins/heart.gif.
Hero calls t30, MP1 calls t30, MP2 calls t30, CO calls t30, <font color="#666666">1 fold</font>, SB completes, BB checks.

Flop: (t180) 4/images/graemlins/club.gif, T/images/graemlins/heart.gif, A/images/graemlins/heart.gif <font color="#0000FF">(6 players)</font>
SB checks, BB checks, <font color="#CC3333">Hero bets t125</font>, MP1 folds, MP2 folds, CO calls t125, SB folds, BB folds.

Turn: (t430) Q/images/graemlins/heart.gif <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">CO bets t300</font>, Hero calls t300.

River: (t1030) 2/images/graemlins/spade.gif <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">CO bets t920 (All-In)</font>, Hero folds.

Final Pot: t1950


My thoughts:

Pre-flop: Of course, an argument can be made to fold, but I like to play any small or medium pair cheaply from any position in the first two levels.

Flop: I didn't want it to get checked around with 6 players in the hand. I bet 125 because I thought it would clear out anything but an Ace or a flush draw. Figured I would re-evaluate on the turn if I got called.

Turn: One caller, that's good. Flush on the board, that's bad. OOP, I figured I check and see if I can define his hand by his bet (or check). Looking back, I'm pretty sure this was a mistake. He bets about 3/4 pot, and I can't figure what that means. But my gut says he made his hand. I call with redraws to the full house (9 outs?), although I now see I may not have had odds.

River: Still don't know what to do, so I check. I fold to his push, convinced I'm beat.

I know I played this poorly, so I'm wondering what anyone else does from start to finish, since I think I made mistakes on all streets. How many of you push, and where? I'm looking for someone to tell me WHY they would take another line, please, because I'm trying to learn.


Thanks and gl

Sean

[Freudian]

When you call the turn bet, I don't see how you can fold on the river.

Fair enough, do you think this is a situation in which barring an absolutely 100% read of flush (which is nearly impossible at the $5's), I can't lay this down?

[Freudian]

It depends. It is a pretty scary board. But when everyone limps in there is a pretty big chance someone hit a two pair or even a pair.

At the 5s I probably would call this river no matter what and it is a much easier decision when he pushes instead of betting 200.