OVERCALLS:
This week our topic is about so called 'overcalls' on the river.
An overcall is a call on the river after player A made a bet, player B called this bet and now it's Heros turn whether he wants to make a call (overcall) or not. This is a special situation because now Hero has to beat player A AND player B instead of only player A.
You may now ask yourself why this is a special situation. The problem is that player A might have bluffed which we can beat with a marginal hand but the chance that player B has a bluff as well is nearly zero and so we need a better hand to call in this situation.
Many opponents don't understand this concept and so we can exploit it.
++++++++++ HAND 1 ++++++++++
Let us take a look how we can exploit the fact that many don't understand this concept. (For example they overcall with marginal hands like 3rd pair or A-high.)
If we are in the middle position (positions at the river: player A, Hero, player B) with a good hand with which we aren't sure whether we really have the best hand we can call the bet of player A to get an overcall from player B.
To make it more clear: The sample hand is from the micro limits and so nearly all players are weak and passive and see too many showdowns with marginal hands.
Preflop: Hero is UTG with A♠, A♥
Hero raises, 2 folds, MP1 calls, MP2 calls, MP3 calls, 3 folds, BB calls.
Preflop: With AA we have an easy play preflop and 4 weak players are calling our raise.
Flop: (10.50 SB) Q♥, 8♠, 4♣ (5 players)
BB bets, Hero raises, MP1 calls, MP2 calls, MP3 calls, BB calls.
Flop: BB donkbets (A bet into the aggressor from the previous street.) into us and we raise immediately get money into the pot with probably the best hand and to protect our hand from draws (We try to get headsup with BB to improve our chance of winning the hand.).
Turn: (10.25 BB) 7♥ (5 players)
BB checks, Hero bets, MP1 calls, MP2 calls, MP3 calls, BB calls.
Turn: No one folded on the flop which again shows us that we are playing against weak players. The 7 may have helped someone but nevertheless our hands still has a great chance of being ahead and so we bet the turn again to get calls from worse hands and to protect again from draws.
River: (15.25 BB) K♠ (5 players)
BB bets, Hero calls, MP1 calls, MP2 calls, MP3 calls.
River: Now we are at the most interesting part of the hand. The weak passive BB donkbets again into us (He seems to be unreasonable and it looks like that he isn't able to judge his hand strength correctly.) and we have to take a decision.
We can't fold in such a big pot but the chance of still having the best hand is too low to raise as well.
KQ, K8 and other two pair combinations are possible and worse hands will often fold to our raise.
If we just make a call here we may induce 3 overcalls from the players behind us and this way we lose the minimum against better hands like two pair or better and win the maximum against worse ones like small pairs or even with just a 4 because they didn't understand the concept of overcalls.
In the end we should win often enough to make this play profitable because BB may misjudge the strength of his hand and bet with just a Q.
Final Pot: 20.25 BB
++++++++++ HAND 2 ++++++++++
A classical example to induce overcalls is where we have a straight with just one of our holecards and where we can't be sure to hold the best hand.
Preflop: Hero is BB with J♠, T♠
2 folds, UTG+2 raises, 2 folds, MP3 calls, CO folds, BU calls, SB calls, Hero calls.
Preflop: Hero has an easy call with JTs here because this hand plays very well in multiway pots.
Flop: (10.00 SB) K♥, Q♥, 4♦ (5 players)
SB bets, Hero calls, UTG+2 calls, MP3 raises, BU calls, SB calls, Hero calls, UTG+2 calls.
Flop: On the flop we hit an oesd where every 9 or A completes our straight draw. e don't raise here because we have to hit one of our outs to win the hand and we get more value by letting more oppoent to join the pot instead of isolating us against SB with the worse hand.
Additionally the A 
and 9 outs aren't clean because they complete a possible flushdraw.
Nevertheless we have an easy call on the flop.
Turn: (10.00 BB) T♣ (5 players)
SB checks, Hero checks, UTG+2 checks, MP3 bets, BU calls, SB calls, Hero calls, UTG+2 calls.
Turn: On the turn we hit one of our pair outs which grants us maybe some additional outs. On the other hand we could now be a big underdog against AJ. But again we shouldn't be to pessimistic because on average we have enough outs to proceed in the hand but we should stay passiv.
River: (15.00 BB) 9♦ (5 players)
SB bets, Hero calls, UTG+2 calls, MP3 calls, BU folds.
River: On the river we made or straight and SB suddenly bets again. Mot of the time he has the straight as well. Still we don't have the best possible straight (AJ beats us.) and we would scare away AQ, pair of kings or other worse hands with a raise which would probably call in such a big pot to just one bet we should not raise here but just call to induce overcalls.
Again we should win the most over the long run with our play.
Final Pot: 19.00 BB
++++++++++ HAND 3 ++++++++++++
The same counts for a so called one card flush where we only use one of our holecards for the flush and where we don't have the best possible flush.
Preflop: Hero is MP2 with K♥, Q♣
Hero raises, MP3 folds, CO calls, BU calls, SB folds, BB calls.
Flop: (8.50 SB) A♥, T♣, 2♣ (4 players)
BB checks, Hero bets, CO calls, BU calls, BB calls.
Flop: Against 3 opponent we can make close continuation bet
Turn: (6.25 BB) K♣ (4 players)
BB bets, Hero calls, CO calls, BU calls.
Turn: On the turn we have to call with our pair and the outs to a straight or flush.
River: (10.25 BB) 4♣ (4 players)
BB bets, Hero calls, CO calls, BU folds.
River: On the river we have the 2nd best flush but nevertheless BB is betting this scary board which shows much strength. Because of this we just call here to again induce some overcalls. With a raise we would scare worse hands away which may have called for one bet.
Final Pot: 13.25 BB