If you can find a path with no obstacles, it probably doesn't lead anywhere. (Frank A. Clark)

After a crash course in 4-bets it is time for a few examples. The following is very standard:

Hand 1: Cold 4-bet as a bluff
***** Hand History for Game 1111111111 ***** (Party)
$600.00 USD NL Texas Hold'em - Monday, January 10, 09:24:23 ET 2011
Table Table  178204 (Real Money)
Seat 6 is the button
Seat 1: Player1 ( $1284.01 USD ) - VPIP: 30, PFR: 23, 3B: 8, AF: 1.7,
Seat 3: Player3 ( $630.96 USD ) - VPIP: 54, PFR: 24, 3B: 7, AF: 1.1,
Seat 6: Player6 ( $645.00 USD ) - VPIP: 25, PFR: 19, 3B: 6, AF: 2.0,
Seat 5: Player5 ( $1338.75 USD ) - VPIP: 22, PFR: 18, 3B: 7, AF: 3.0,
Seat 2: Hero ( $619.05 USD ) - VPIP: 21, PFR: 16, 3B: 7, AF: 2.7,
Seat 4: Player4 ( $1097.49 USD ) - VPIP: 22, PFR: 12, 3B: 7, AF: 1.8, Hands: 31081
Player1 posts small blind [$3.00 USD].
Hero posts big blind [$6.00 USD].
** Dealing down cards **
Dealt to Hero [  Ks Qs ]
Player3 folds
Player4 folds
Player5 raises [$18.00 USD]
Player6 folds
Player1 raises [$63.00 USD]
Hero raises [$129.00 USD]
Player5 folds
Player1 folds
Hero wins $219.00 USD from main pot

The 4-bet bluff here is especially good when you have blockers. If they shove I of course fold. Most  players will only shove with QQ+ and AK. With KQ you actually remove a lot of the combinations of these hands. There is still 6 combinations of AA. But the rest go way down: KK is reduced to from 6 to 3 and the same with queens. AK is reduced from 16 to 12. So overall the hands that will play back is down from 34 to 24! But it is suited and you make your hand into a bluff - yeah it is a nice looking hand but you can't call and if you fold it doesn't matter it was suited. Notice that the only thing that isn't 'perfect' in the above set-up is the stack sizes for the initial raiser and the small blind. They both have more than 200 bb. Which would suggest that the small blind probably has a stronger hand than normal to 3-bet. If they have seen you pull this stunt a lot it stop beeing so effective. Exercise: How much fold equity (combined for the two) do you need to make this play?

Hand 2: Dealing with shorties

***** Hand History for Game 1111111111 ***** (Party)
$400.00 USD NL Texas Hold'em - Monday, January 10, 03:20:48 ET 2011
Table Speed 1780813 (No DP) (Real Money)
Seat 6 is the button
Seat 3: Player3 ( $152.84 USD ) - VPIP: 35, PFR: 5, 3B: 2, AF: 1.5,
Seat 5: Player5 ( $728.90 USD ) - VPIP: 23, PFR: 19, 3B: 7, AF: 3.7,
Seat 1: Player1 ( $410.00 USD ) - VPIP: 25, PFR: 20, 3B: 9, AF: 2.4,
Seat 4: Player4 ( $455.40 USD ) - VPIP: 19, PFR: 15, 3B: 7, AF: 3.2,
Seat 6: Hero ( $565.50 USD ) - VPIP: 21, PFR: 16, 3B: 7, AF: 2.7,
Seat 2: Player2 ( $140.00 USD ) - VPIP: 31, PFR: 30, 3B: 10, AF: 4.2,
Player1 posts small blind [$2.00 USD].
Player2 posts big blind [$4.00 USD].
** Dealing down cards **
Dealt to Hero [  8h 8s ]
Player3 folds
Player4 folds
Player5 raises [$12.00 USD]
Hero calls [$12.00 USD]
Player1 folds
Player2 raises [$37.00 USD]
Player5 folds
Hero raises [$553.50 USD]
Player2 calls [$99.00 USD]
** Dealing Flop ** [ 3c, 2h, 4s ]
** Dealing Turn ** [ 6h ]
** Dealing River ** [ 2s ]
Player2 shows [Ah, Qc ]
Hero shows [8h, 8s ]
Hero wins $425.50 USD from main pot
Hero wins $291.00 USD from main pot

Shortstacker are not as big a problem as they used to be. Mainly due to the fact that most sites now have a 40 big blind minimum policy - Thank you!! But they still exist and on Party Poker they are mainly very loose aggressive guys from Spain (they must have a short stacker forum or something). These guys live from fold equity! Most players fold too much against these guys. In the above example he will squeeze a lot with a very wide range. Probably all pairs and broadways. So jamming it for 140 with a lot of deadmoney in the pot is absolutely obligatory imo. I think he will call with top 12% of his range. Against that range I have 47% equity - making it a very easy shove.
Toying with how much fold equity and equity you need against shorties is a very good exercise - don't be shy :)

Hand 3:  Standard spot
***** Hand History for Game 1111111111 ***** (Party)
$400.00 USD NL Texas Hold'em - Monday, January 10, 12:35:37 ET 2011
Table Table  178994 (No DP) (Real Money)
Seat 1 is the button
Seat 2: Player2 ( $174.90 USD ) - VPIP: 52, PFR: 3, 3B: 2, AF: 1.0,
Seat 4: Player4 ( $425.90 USD ) - VPIP: 25, PFR: 20, 3B: 9, AF: 2.4,
Seat 6: Hero ( $400.00 USD ) - VPIP: 21, PFR: 16, 3B: 7, AF: 2.7,
Seat 1: Player1 ( $409.60 USD ) - VPIP: 23, PFR: 19, 3B: 8, AF: 2.7,
Seat 5: Player5 ( $501.50 USD ) - VPIP: 40, PFR: 10, 3B: 3, AF: 2.9,
Seat 3: Player3 ( $476.80 USD ) - VPIP: 28, PFR: 22, 3B: 10, AF: 2.5,
Player2 posts small blind [$2.00 USD].
Player3 posts big blind [$4.00 USD].
** Dealing down cards **
Dealt to Hero [  As Ac ]
Player4 folds
Player5 folds
Hero raises [$12.00 USD]
Player1 raises [$36.00 USD]
Player2 folds
Player3 folds
Hero raises [$76.00 USD]
Player1 raises [$373.60 USD]
Hero calls [$312.00 USD]
** Dealing Flop ** [ Jc, 4s, 6d ]
** Dealing Turn ** [ 7s ]
** Dealing River ** [ 3h ]
Hero shows [As, Ac ]
Player1 shows [Ks, Ah ]
Player1 wins $9.60 USD from main pot
Hero wins $803.00 USD from main pot

Aces are always good. Against some players it makes a lot of sense to just flat big pairs preflop to a 3-bet. But imo not aces! Aces are so much better than all other hands and the chance to get it all-in preflop should almost always be utilized. Out of position I - as you all know by know - never call a 3-bet: It is 4-bet or fold. So here the choice is easy. My opponent in the hand is also 3-betting a depolarized range. If it was polarized (very good and speculative but not the middle value range) flatting it something you should consider in position. I often flat AK and QQ (like half the time) and seldom KK (20%) and even rarer with AA (5%).  

A good exercise with Pokerstove: Against what range can you 4-bet get it in with QQ - does your opponent need to have JJ? TT? In his shoving range to make it profitable?