continuation bet check-raised on 200NL

[jacknine]

200NL, full ring ... No reads on Villain.

UTG+2 ($208.25)
MP1 ($217.25)
MP2 ($200.75)
Hero ($181.25)
CO ($41.25)
Button ($67.50)
SB ($70.25)
BB ($74.00)
UTG ($286.50)
UTG+1 ($198.00)

Preflop: Hero is MP3 with K[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/club.gif[/img].
<font color="#666666">1 folds</font>, UTG+1 calls, <font color="#666666">1 folds</font>, MP1 calls, <font color="#666666">1 folds</font>, <font color="#CC3333">Hero raises to $12 </font>, <font color="#666666">4 folds</font>, UTG+1 calls $10, <font color="#666666">1 folds</font>.

Flop: ($29) Q[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
UTG+1 checks, <font color="#CC3333">Hero bets $18 </font>, <font color="#CC3333">UTG+1 raises to $40</font>

What to do here? I was quick to fold. Anybody disagree with that?

What about the pre-flop raise ... My standard opening bet is 4BB + 1BB for every limper before me.

What about the continuation bet on the flop. Too big? Too small? Should I have bet here at all, or just checked to see the turn for free?