There are a lot of so called "tells" in a poker game where you if you have the right skill set can tell if a player have a good or bad hand.

Which is the one you look for the most?

For me it is easy tell when a player looks a lot and seem to count his/hers chips. Then they usually have a good hand.

With bad hands a common tell is that the player try to represent strength to make an illusion that they have good cards.