I refer to fishes as passive fish and donkeys as aggro donkeys.
So how to exploit them?
With passive fish = Loose passive. 50+ VPIP and very low PRF 5
I would use a tight aggressive style.
So play a value range that will beat their range. Bet and raise for value, never bluff!! Bluffing these types of players is just spewy as they will call with their pocket deuces no matter what is on the board. Beware on the river if they call both flop and turn and then raise on the river. Also beware when they start playing aggro.
With aggro donks = Loose Aggressive = Lag tards. VPIP 50+ and a very high PRF 40
I would use a tight passive
So play strong value range, limp hands that cannot stand a 3bet preflop but you want to play in position. E.g, SB you know if you raise this donk is going to 3bet you so limp, you can either call or shove. (The shoving is used as a trap so only do this with a premium hand) 3bet tighter and call against raises in position, only if it is raised by the donk. Raise turn with strong hands and bet river. Assume they may be bluffing a lot (if you have enough reads on that donk) If you have the nuts or close to it call on the flop. So that means x/c or just call if he donks. Then raise on the turn as he will more than likely call with worse. Make sure to make notes on the donk and with practice you will be able to know what move to make against them.
EDIT: Make sure you have enough hands to make sure they are in fact fishes or donks, I like to have 500+ hands to get a more accurate read.
Hope this helps, GL
I would rather play right and lose than to play wrong and win
RoW Champ 2014.
That is kind of too large of a question to answer but will just list a few generalities.
I look for players that play too many hands, play passively, do not play position, over bet or overplay hands. In general you are looking for things that you know are not optimal plays done consistently.
Once you found them, just try to replicate those situations where a player will play incorrectly and lose their chips.
i tend to look for patterns and variances in players when they are at my table, i had a good example of this yesterday during the partypoker freeroll, i was at a table with a player whose regular opening bet ranged from 2.5 to 5x the BB when opening in early position - i noticed he was picking up around 30% of the blinds using this variance and in fact after closer inspection - i was certain that he was using a wide range of hands - after around 70 hands, i started to test my theory as i wanted time to see how he played out against the rest of the table and was simply being patient, waiting for hands that i felt would play well against him.
The end came after gradually reducing his 15.5k stack down to around 6k when he then started jamming..i shoved AK diamonds and he called off 67cl - board ran out with a flopped Ksp and it was over.
Keeping notes also works for me - there are a few players on CC at present which interest me hugely so i am working on those "persons of interest" - players who are very good i might add!
I disagree with EvertonGirl, when playing with passive fish it is best to play a LAG style over a TAG style if your post flop skills are good. They tend to play very straight forward which allows you to steal a lot of pots and you can easily tell when you are beat(aka they start betting) so I'd play about the top 30-35% of hands with them.
VS aggro donks, a lot of the hands you play should be determined by the stacks behind for both you and the donk.
With 10x their preflop bet behind, call with any pocket pair.
20x their preflop bet behind, call with most suited connectors(56s+) and high suited hands(Axs, Kxs), be careful not to get to attached to a high pair though.
30x their preflop bet behind, call with most gapped suited connectors(68s+).
Other than that, only call with broadway hands/high pocket pairs(JJ+).
Vs. aggro donks, you also need to know how they react to 3bets, if they call a lot of 3bets then be sure to 3bet if you have AQo+, AJs+, KQs+, QQ+. But, if they fold to a lot of 3bets then throw bluffs into your 3bet range such as JTs, JJ, K9s+, etc.
Against these players never bluff, never A semi-bluff can be given from time to time, but never plain bluff. It's because? Because for fish there is no fold / word button! He thinks he's always going to hit the river with the card that will help him! And every once in a while it hits !! Bluff only against players who have the ability to fold a marginal hand.