Don't lie, cheat, steal, or cut corners- ever.
Never give the appearance of being unenthusiastic. Even if you got up at 5 am to come to work with minimal sleep. Even if that's been happening regularly for an entire month.
Always be demonstrably humble, particularly as a CA-1. No one likes teaching or working with a chirpy CA-1 who says "of course" "I know" and God forbid "MD aware" when they know not their own cluelessness.
Get good at basic technical skills as soon as possible. People will be quick to judge you on how smoothly you can place an IV, a-line, ETT, etc.
Don't cause delays. If it's a 7:30 am OR case, you should be the one pushing the nurses to let you take the patient in at 7:27. If that means coming in extra early to set up, or calling the patient the night before to have the pre-op interview, do it. Be aggressive and enthusiastic about getting the work done, and everyone will appreciate it.
Always be punctual. Be quick to relieve people on call. You would be surprised how soon word spreads that you are "slow". No one will give you credit for being 5 minutes early, but everyone will notice and hate you for being 5 minutes late.
Avoid assumptions. Don't assume that just because a tech set up your a-line pressure bag that he bothered to make sure all the connections are tight, and that the thing is connected to your monitor, and zeroed. If you didn't do something yourself, always verify. Avoid using other resident's drugs. Don't let someone else's mistake become your own.
Don't hide. If you're free and available, ask your supervisor if there's anything you can do.
Don't fight with nurses. It's never worth it.
Learn everyone's name. Techs, nurses, surgical colleagues, the janitor.
Read regularly.
Remember House of God, they can't hurt you forever. Residency sucks, but eventually it ends.
Doing these things well all the time is almost impossible, especially early on. These are the things that get noticed, however, and will form the basis for other's opinion of you. Do the best you can, and good things will eventually come your way.