Knowing your opponents is beating your opponents. When you are playing low stakes you probably only think about exploiting the fish, because your good hands are paid off anyway. When you are moving up, your thought process should become more sophisticated, since players are better on average. A common thought (or mistake) by many players when moving up is to avoid the regulars, because they are afraid of them (for some reason) or they think it is more profitable to focus on the fish. I think both arguments are flawed. Especially at low-mid stakes many regulars do make consistent errors and we call them leaks. When you are able to discover these leaks, then you are able to pound on your opponents’ weaknesses and increase your winrate.

I wrote this article on my low-mid stakes experience (50-100NL). Me too, when I started playing these stakes, focused more on the fish then on the regulars. But at some point of time (I don’t remember exactly why and when), I shifted my focus to the regulars, by making detailed notes on lines that they took with particular hands. I soon discovered that many regulars exhibit tendencies that are (very) exploitable. Moreover, this analytical framework led to more comprehensive strategies to exploit the fish. In the next few paragraphs I describe the most common leaks that I encountered in low-mid stakes games. These are not leaks, which belong exclusively to regs or fish or to particular type of players. Nits can get crazy on a 996 flop with air, and loose players may only raise with trips on the same board.

Hunting:
The tendency to play flush draws and straight draws passively and to call bets, while not getting appropriate expressed odds. You can exploit hunters to make them pay for their draws.

Calling too light:
Calling too many streets with marginal hands, for instance 2nd or 3rd pair consistently against various types of players. By value betting strong and bluffing less you can exploit this.

Playing too tight:
Only playing good hands and only betting good hands. Very transparent betting lines. Also surrendering their blinds too easily (if their fold verus a steal is > 83% you are obliged to steal with any 2 cards). You can bluff and steal more often against these tight players.

Playing too lag:
Making too many moves and carry their moves too long. 3 barrel with AK on missed boards, or 3 barrel with air on paired flops. It is profitable to slow play against opponents who display this behavior.

1 bet bluffing:
Will only bluff bet once and will give up after that. Never or rarely bluff more than one street. You can float more often and pick up the pot on later streets against 1 bet bluffers.

Timing tells:
These are especially true for bad players. Instabet or raise means: monster. Hesitation means: marginal or weak hand. Instacalls on earlier streets are often a sign of a drawing hand. These timing tells may have the oppositie meaning with thinking regulars, who may wait on purpose before getting it in with the nuts.

Bet sizing tells:
These are again especially true for bad players. Big bet means big hand and weak bet means weak hand. Combining these with the previous timing tells, you should be able to dodge the fish’s big hands.

Stealing too much and folding too much to resteal:
Players, that try to steal much, but often fold (>70%) to a resteal/3bet. Frequently 3 betting against these players is very profitable.

Playing fit or fold:
A player’s tendency to only continue post flop when his hand hits the flop. Since in Holdem you miss the flop more often than you hit it (2 to 1), this tendency can be exploited by isolating and consistent continuation betting. A strong indication of playing fit or fold is when a player has a fold to cbet statistic of around 67%.

Limp folding:
Players who limp in, but fold to a raise, are donating money. Punish them by constant raising, till they adjust.

Unable to fold an overpair:
Players who are unable to fold their overpair are the perfect opponents for set hunting or playing suited connectors. I am not saying you should always fold your aces if you meet resistance. However, in many cases it should be obvious you are beaten.
Playing marginal hands without the implied odds:

The tendency to play hands with implied odds (e.g. small pocket pairs), when these are not sufficient. For example, first calling deuces in the big blind against a solid button raiser (in this example a set will not be paid off enough on average in order to set hunt).

You should always take the situation into account, before assigning a villain’s play as a leak. So may calling 3 streets with 2nd pair correct in a specific situation against a specific opponent. Therefore defining your opponents’ leaks requires judgment and history, since leaks are errors which your opponents make consistently, or at least regularly.

This article may be updated in the future, since in my development as a poker player, I may discover new situations to exploit and more leaks. Also, readers can contribute to this article. Therefore, I would like comments and discussion on this article.