Make sure that your instruments are properly set up and intonated, and tune before every take.
Be patient. Recording sessions involve a lot of waiting around.
It may be too late for this if you're recording tonight, but have a plan. Know what you want to record and make sure that it is well rehearsed. In the studio, on the clock, is not the time or place to be working out tunes.
Play when you are told to play. Stop playing when you're told to stop. You don't want to be noodling around while the engineer is trying to position mics or get levels on another instrument.