Part: Part Five - Betting Before the Flop

A light three-bet

Pre-flop
Blinds 100 / 200Pot 900 (4.5 BB)BBA♦5♦● 25,000 (125 BB)YOUto actBTN● 25,000 (125 BB)Wide buttonraises 500 (2.5 BB)SBfoldsD

A loose button that steals constantly opens to 500. You're in the big blind with A♦5♦.

A wide-stealing button opens to 500 (2.5 BB); you hold A♦5♦ in the BB. Best?

WhyThree-bet as a light re-steal. Against a button opening far too wide, a three-bet folds out most of his range, and A-5 suited is an ideal bluff: it blocks his strong aces and still flops flushes, straights, and pairs when called. Flatting out of position is the weakest option.
What happensYou three-bet to 1,800 (9 BB); the wide button folds.  You win it pre-flop.
Against a button stealing too wide, a light three-bet with a blocker hand (A-5 suited) takes the pot before the flop - an essential way to fight back from the blinds.

Three-bet light against players who open too wide - pick blocker/suited hands that fold out their range and still play well when called.