K9o from BB, flop TP + overcard

[bozlax]

The call on the river was easy for me...the question is, should I have bet out the flop and turn? Am I betting for value, here, as I believe?

Party Poker 0.5/1 Hold'em (8 handed) converter

Preflop: Hero is BB with 9[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/club.gif[/img].
UTG calls, <font color="#666666">3 folds</font>, CO calls, Button calls, <font color="#666666">1 fold</font>, Hero checks.

Flop: (4.50 SB) 6[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">Hero bets</font>, UTG folds, CO calls, Button calls.

Turn: (3.75 BB) 3[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, CO calls, Button calls.

River: (6.75 BB) 4[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">CO raises</font>, Button calls, Hero calls.

Final Pot: 12.75 BB