Part: Part Six - Betting After the Flop

Pot control

Flop
Heads-upPot 1,300 (6.5 BB)KJ5BTNAJ 25,000 (125 BB)YOUmiddle pair, decent kickerMP 25,000 (125 BB)OpenerchecksD

You called a middle-position open on the button with A♣J♥. Flop K♠ J♣ 5♦ - you have middle pair (jacks) with an ace kicker. He checks.

Middle pair on a king-high board, in position, he checks. Best?

WhyCheck behind. Middle pair is a medium hand: betting bloats the pot against the better kings and gets little from worse. Checking controls the pot, takes a free card with your kicker, and keeps his bluffs in for a later street.
What happensYou check behind.  Pot stays 1,300 (6.5 BB).
Turn
Heads-upPot 1,300 (6.5 BB)KJ58BTNAJ 25,000 (125 BB)YOUmiddle pairMP 25,000 (125 BB)Openerbets 900 (4.5 BB)D

Turn 8♥ - a blank. Now he bets.

After you checked back, he leads the turn. With middle pair, best?

WhyCall. You kept the pot small on the flop precisely so you could afford to bluff-catch one bet here. Middle pair with an ace kicker beats his bluffs and worse pairs; calling one bet is fine, but you won't be stacking off.
What happensYou call; the river checks through and your jacks are good.  You win a small, controlled pot.
With a medium hand you checked back to control the pot, which let you comfortably call one turn bet as a bluff-catcher. Pot control keeps medium hands cheap and decisions easy.

Check back medium made hands to control the pot - keeping it small lets you realize showdown value and bluff-catch cheaply instead of bloating with a one-pair hand.