I am by far from being a professional in the game of poker, but I am sure that I have played a few professionals and taken their chips by surprise just by keeping a straight face and showing no tell signs. (But, that can help while bluffing.)
I guess that would be; don't fidget or move around a lot with either a good or bad hand.
I have to wear a loose fitting shirt in live poker, because my heart gets to thumping when I know my hand will take the pot.
What works for me in live poker; other than keeping light conversation and goofing off occationally just to keep the crowd from being so serious in the game, is drinking a few mixed drinks or beer to get into a relaxed posture for the game.
I have watched newbies on a televised poker tournament, on a couple of occations, get so nervous they would be shaking while moving their chips or looking at their cards. That is usually a sign of; "Hey, look at me, I have a big pair in my hands. Call my bet, please."
Having a relaxed form and keeping a straight face when the cards are delt is about the best thing I can think of, other than playing your cards right and watching how other players play as well.
Oh, and then there's the position; I'm not one to scrutinize player position, but I am slowly taking it into consideration. Where a player is sitting in correspondence to the dealer button also has a lot to do with how you're betting or how others will bet.
Most of the time the big and small blinds don't like to be forced out of their chips, so they may call or re-raise just to keep from getting them taken away.
There are many variables to think about while playing live poker, but the few I've mentioned is from personal experience.
Does anyone else have something to add in?
You don't have to make it as long as I did, but I'm somewhat of a writer and can't help going on and on and sometimes in detail.