This is where make it your recording. This is the time to let all your spirit, character and personality shine through, because it's much harder to create that afterward. Whether recorded in a live concert or in the studio, if the performance is flat and lifeless, don't plan on being able to "fix it in the mix." It also helps the performance atmosphere in a session if you arrive with a jolly good attitude, as exuded here by Ron Pen. (Costumes are optional.)
If it's your first recording session, it can seem a little daunting because the studio is very quiet and everyone present is listening and judging your performance on each take - you want the best take, after all. Just relax and do your best.