Classify your players

It's important to develop a classification system for your players. Some people use animals, others use symbols, others use words. I think it's important to use a system that works for you, however, if you can associate a person with a word and a color and a shape, or an animal, you're probably going to remember easier. All you have to do when you look at someone's avatar, or face, or screenname, or whatever you have to look at, is visuallize that animal or symbol. Once you are comfortable with a classification system, it will be much easier to know how they play.
I like to use colors and shapes. The colors, will classify preflop play, and the shapes will classify post flop play. And if my opponents are barely fitting that classification, I'm using "dark color, or "light"l color, or big shape, or small shape. if they're somewhere between, you can have redish blue, or a square like circle.
Here are the colors and shapes I use
Green - tight passive
blue-loose passive
red- tight aggressive
yellow- loose aggressive
In general for tournament play I want to avoid the yellow and red players. Yellow to me means caution and red means stop.
for postflop play here are the shapes
circle-tight passive
square- loose passive
octogon(like a stopsign)- loose aggressive
triangle-(think caution sign)-tight aggressive
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The loose aggressive before the flop is usually less dangerous. You can certainly call a raise with a loose aggressive preflop player if you can outplay him after the flop as long as you use caution and aren't going to make a significant risk without understanding it. if you're facing a raise from a tight aggressive player, it's pretty likely that he's going to be difficult to play as he'll have a strong hand. He might give it up, and be passive after the flop, but he's a lot more likely to have something after the flop. When you're looking at the styles after the flop, you're going to want to avoid bluffing a loose aggressive player. You can call them down with a big hand, but you cannot make a move without a hand if they are loose aggressive post flop.
However, if they are tight aggressive, you can attempt to raise them, or call to represent a flush draw, and bluff if a scare card hits, as long as you are cautious and willing to get out if you're wrong, and as long as you consider their preflop tendancies. Someone who is loose preflop and tight post flop is perfect to try to bet the flop to steal.

The more you are comfortable with this type of classification, the easier your decisions will be. Soon you'll say, there's a lot of green players at the table, I need to go red to pick apart their blinds. Or "players are acting blue, I should try to see a lot of flops, so I can bet and get paid off by the squares, or let an octogon do the betting for me when I hit."
TYour mind qwill be able to think in very simplistic terms that will allow it to be very logical, and you can spend your time worrying about the blind structure, the tournement payout, and what type of moves you can make now, and willneed to make later.

By using a system for player classification, you will noticebly improve your game, as long as you don't get too carried away with your bluffs and continue to play any 2 just because they're a green circle. They may be sophisticated enough green circles to realize that you adapt to players styles, and they might change their game based on their perception of you. Also, just because you CAN make a move, doesn't mean you should all the time. You also ideally want to see some verification that the players continue to play the same way, and that they're not players who mix things up. Sometimes players will be green circles without much of a hand, but when they have a hand they'll be red octogons.
But if you gradually add a classification system without changing the way you play too dramatically, until you become comortable with all ocf this, you should find yourself winning a lot more, or at least accumulating chips more, and getting your money in better.