Part: Part Five - Betting Before the Flop

Isolating a limper

Pre-flop
Blinds 100 / 200Pot 600 (3 BB)BTNA♣J♦● 25,000 (125 BB)YOUto actMP● 25,000 (125 BB)Weak limperlimpsSB● 25,000 (125 BB)posts 100 (0.5 BB)BB● 25,000 (125 BB)posts 200 (1 BB)D

A weak, passive player limps in from middle position and it folds to you on the button with A♣J♦.

A weak limper, and you hold A♣J♦ on the button. Best?

WhyRaise to isolate. A-J dominates a limper's weak range, and raising gets you heads-up and in position against a player who has shown weakness. Limping behind invites a multiway pot and squanders your edge over the limper.
What happensYou raise to 900 (4.5 BB); the limper calls, the blinds fold.  Pot: 2,100 (10.5 BB).
Flop
Heads-upPot 2,100 (10.5 BB)A♦7♣3♥BTNA♣J♦● 25,000 (125 BB)YOUtop pairMP● 25,000 (125 BB)Weak limperchecksD

Flop A♦ 7♣ 3♥ - top pair, good kicker. The limper checks.

Top pair, good kicker, heads-up and in position. Best?

WhyBet for value. You isolated to play exactly this pot - heads-up with the best hand against a weak player. Bet to get value from worse aces and pairs.
What happensYou bet 1,200; the limper calls then gives up the turn.  You win.
You raised to isolate a weak limper, got heads-up in position with a dominating hand, and value-bet your flopped top pair. Isolation raises turn a limper's weakness into your profit.

Raise to isolate weak limpers with strong, dominating hands - get heads-up and in position rather than limping along into a multiway pot.