Pre-Flop actions - yours and your opponents

Your own actions pre-flop are determined by the starting hands list. As a beginner you must strictly follow the recommended actions and take any raise by your opponent serious, meaning you cold-call 2 bets only when you have a very good hand. There is one exception: if you have the big blind or small blind position and everybody has folded but the cut-out or button raises. This could be an attempt to “steal the blinds” and the raiser must not necessarily have a strong holding. In this situation, if you have a decent holding for a heads-up game (like A9o) you should not call, but re-raise and bet into the aggressor after the flop. You want to show the aggressor that you have “read” his move and that you are not giving in without a fight. Otherwise he will try that move over and over again and it will cost you. This is called blind defense. Of course, if you have a very bad hand, dump it.
Very often the aggressor will back off if he encounters a re-raise and fold after you bet the flop because the flop has missed him. Be careful, though, when you get resistance even after the flop. He might after all have a good hand.

Evaluating your opponents pre-flop actions

If all your opponents would stick to the starting hands list like you do, it would be relatively easy to guess what the other guy might be holding. However, in the low limit games your opponents play rather loose, meaning they play all kinds of hands. That means it is hard to guess what they hold, their hand range is wide.
At the same time the hand range of your opponent is usually wider when he is in a late position. A call “under the gun” indicates a strong holding. A raise is also to be considered in relation to where it came from, meaning a raise from UTG (“under the gun”) is to be respected more than the button’s raise. Basically, you go by the concept that you cold-call a raise only with very good hands or when many players have already called the raise and the pot is very big, meaning you get good pot odds. You still need a hand that is strong against multiple opponents (like a pocket pair or two suited connectors like QJs) to call in such a situation.

The Small Blind only has to put half a small bet in, so if he calls he does not need quite such a strong hand. If the Big Blind checks he can have any hand. A raise from the Big Blind or Small Blind is serious: they both know that after the flop they have to act early (although this can be an advantage sometimes).