UTG smells kinda fishy. Limping a lot, raising nothing. But fairly aggressive after the flop.

Full Tilt No-Limit Hold'em, $0.50 BB (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

UTG ($57.35)
UTG+1 ($38.75)
MP1 ($48.30)
MP2 ($33.25)
MP3 ($20)
CO ($42.75)
Button ($34)
SB ($50)
Hero ($50.50)

Preflop: Hero is BB with 3, 9.
UTG calls $0.50, 1 fold, MP1 calls $0.50, 4 folds, Hero checks.

Flop: ($1.75) 9, T, 9 (4 players)
Hero bets $1.25, UTG calls $1.25, MP1 calls $1.25.

Turn: ($5.50) K (4 players)
Hero bets $4.2, UTG raises to $8.4, MP1 folds, Hero calls $4.20.

River: ($22.30) 4 (3 players)
Hero checks, UTG checks.

Final Pot: $22.30

One, two ... don't know what to do. I called his minraise hand he checked it down. But what to do against:
- a bigger raise on the turn (maybe $12)
- a big bet on the river (maybe $20)