The more information you can gather on a player the better, up to a point. You want to have a lot of information, but not too much that you can't absorb it quickly. I started keeping notes back before HUDS were widely used. So over time, I've come up with numerous terms that I use to describe different players, styles or tendencies as well as my own shorthand for describing a hand. I can usually describe how a hand played out from pre-flop to the river in a single line.
I usually start with a color code. Then I will use two or three terms or phrases to try to encapsulate my overall impression of a player. I follow that up with two or three hands that I feel are typical for how I think that player plays. Occasionally, I will end with a single line suggesting a strategy to employ for that player, such as "let them lead" or "give them a chance to bluff the river".
One time played a hand where I raised pre-flop with A-Q suited. The small blind called and we saw a flop of Q-9-9 heads up. He checked and then called my two thirds pot bet. After a 2 fell on the turn, he jammed all-in. I usually don't take very long to act. In fact, I play with my time bank turned off and have to activate it if I don't want my hand to be folded after the action clock winds down. In this case, I was considering a fold, thinking that this guy might be holding a 9 and have gotten lucky on me. Then I realized that I had notes on this particular player. I activated my time bank and waved my pointer over that player's name and saw:
FOS
ConRep
Bully bluff shove
> check/call flop, turn - shove river 5x5
*make him show
As soon as I saw those notes, I recalled having played against this guy several days before. Once my notes sparked my memory, I recalled so much more about this player than was in my notes. I made the call. He turned over Q-2. He had Qs and 9s, just like me, but with a 2 kicker against my Ace. The river didn't help him and I took down a huge pot and left this annoying player crippled.
As I said, I had been very close to folding before reading my notes. After reading them, I felt much more confident about calling him. What my notes told me was that this player was full of shit, that he constantly and repeatedly went all-in, and that he often bullied his opponents by bluff shoving. I saw that I had previously seen him him check/call the flop and turn before going all-in on the river five times out of five hands that I watched and that I should call him and make him show me the best hand if he indeed held it.
I typically keep notes on what I consider "bad" players, or when I see obvious leaks in a player's game that I feel like I can exploit in the future. With so many players out there, it's hard to keep notes on all of them. I tend to focus on one or two players at a table that stand out to me or do something that catches my attention. I have a tendency to remember good players, and don't tend to keep notes on them. Besides, I expect good players to switch their game up enough that expecting them to play a certain way from one session to the next might actually get you into trouble.
