The most common bluff in Texas hold 'em is to pretend to have a strong hand even if you don´t.
In order not to be revealed you have to look the same as when betting with a top hand.
If someone raises before the flop but not hit he may increase again to get others to fold.
However, it is dangerous to bluff too often, because opponents can call the bluff and even if they believe that the bluff have an ok hand it will of course come times when someone else has a top hand and then it will be expensive for the one who is bluffing.

The opposite of bluffing a good hand is called slow-play, to play a good hand as if it was weaker than it is.
It can be good when you think you will win but want to get more money into the pot.

Poker tells

Poker tells that tells a good hand

If anyone seems uninterested in the current game but still are in the game, he might try to hide that he has a good hand.
If a player's hands shaking when he put the chips to bet, he probably has a very good hand.
If someone presents false hopelessness it is probably to hide a strong hand.

When someone sees that they have good cards on their hand, it might be that they then immediately look at their chips to see how much they can afford.

Poker Tells that reveals a weak hand

If someone looks challenging at you a long time so they often try to make it appear as if they have a good hand.

Inexperienced players tend to hold their breath when they're bluffing.

poker tells that reveals a "prospective" care With a "prospective" care, we mean here that someone is sitting and waiting for a certain card to get for example a straight or flush. These players have a weak hand right now but have the opportunity to get a strong hand if the right card comes up.
If the flop opens up the possibility that someone may be flush or straight, you should look out for those who check their hole cards.
These people will probably check how close they are to bring in the stright or the flush. It is likely that they then not have got their cards because if they had, they would know this and do not need to check their cards - but they want to see how close they are.

Take time for its views.
Anyone who takes time before he / she calls, and also seems to think of something, probably wondering if are good enough to join in and play.