Although you may not be able to see your opponents online, it is just as easy to read their tells. There are many things your opponent may do to give his hand away. Some of these are:

1. When someone is beat in certain ways such by dumb play, out drawn or bluffed, you should keep an eye on the chat box. Sometimes the player may type obscenities or engage in argument with his opponent. Also keep an eye on which players are "chatting" and note how frustrated they are. If a player continues to complain through several hands they are obviously frustrated and you know their actions will become irrational. In other words he is on tilt which is a good way to make some money. Just wait for a strong hand and bet it like it is weak. The player on tilt will raise you and try to steal the pot. If you are confident that you have won the pot from the flop then it is wise to call his reraises and put him all in on the river. In most cases they will call out of frustration.

2. Sometimes when a player takes a long time to act, they are repreesenting more strength than they actually have. They want you to believe that they are considering raising. Sometimes more advanced players will take a long time when they have a strong hand to provoke a bet to steal the pot. Be sure to take note of any players using this tactic and be cautious when this situation arises with them.

3.If a player is on tilt he may frequently raise pre-flop then fold at the first bet or if someone raises his bet.

4. In online Holdem, if someone checks the flop then calls a raise but then comes out first to bet a small amount on the turn, it is typically a signal that they were on draw but missed and trying to steal the pot. In this case you should re-raise them to see where you are at.

5. If a player is always slow to act then they are usualy playing on multiple tables. This type of player will mostly fold to bluffs and just waiting for premium hands. But if this player calls or raises you, be wary that they have a strong hand.