Our minds are sluggish without proper rest. For the first few weeks on the job, it's essential to be in top form. You're being scrutinized and the way you're perceived in the beginning is crucial. If you have some extra free time between cases, don't just sit in the lounge reading the paper, give another anesthesiologist or CRNA a short break. Nothing makes them love you more than random acts of kindness.
Nobody loves a grouch.
You should come across in the most positive way possible, and the easiest way to do it is by smiling. When we smile, not only do we look happier, we feel that way too. People that are pleasant and upbeat are invaribly well-liked because we all enjoy being around cheerful individuals. Don't complain, even if you feel it's justified. Remember, you're being appraised and you want the image others have of you to be a positive one.