Poker How do you know a player is bluffing or not?

Played in the tournament , I had a medium steak on hand AJ began to raise 3BB one player confirmed . The flop came JKJ. I have raised 5BB he 10BB. I am all in ( thought bluffing ) the player confirms . In the hands of a JK. I lost .
How do I know a bluff ?

Source.

 

you have to observe all players than when you come up against them you may have info on him on how he played in the past. the 3 bet is powerfull most people will let you know by how they bet and what kind of board is out there he had to know you had top pair by the way you bet and he knew he had youi. You have to ask yourself why is he doing this and you will come up with the rt ans 90 percent of the time.

 

Reading players is essential to play poker. When you get so low in stack size, it's not possible, you have to play or die, so first in usually has the advantage.

Those with low stacks and not betting properly clearly give away their hands.

When you want to figure out a bluff, think about preflop betting, position, chip stack size, image of player. You won't always get it right, but you will be almost certain when to get out of the way, and when to smack the bully in the nose.