Tip 6
One or more

Although you would prefer to get some action when you pick up a monster (an extremely good hand for a particular situation) such as A-A or K-K, one of the incentives for raising when you enter a pot is the possibility that you may simply win the blinds right away.  However, this is not the case when one or more players have entered the pot before the action gets to you.  Since other players have shown a willingness to compete for the pot, you need a very good hand to raise.

Some knowledge of your opponents comes in handy here.  If you pay attention when you sit in a game to what types of hands your opponents are turning over, you learn their starting requirements.  (Also observe their position when they enter a pot.)  You may not even need to see their hands; if a player calls 80 percent of the hand before the flop, he is likely to show you just about anything.  Conversely, alarm bells should sound in your head if another player enters his first hand since you sat down – hours ago.  These types of playing styles definitely influence whether some of your hands merit a raise.
  In general, when a typical player has called in front of you, you need a hand such as J-J, A-K, or A-Q suited to raise.  When several players are in, you should elevate your standards even more.  raise with Q-Q or A-K suited.  If one loose player has called, you can raise with some additional hands, such as 9-9, A-Q or K-Q suited.  If the one caller is exceptionally solid, these hand are only worth a call, however, and raises should be limited to J-J, A-K or A-Q suited.