Don't be an asshole. I can't stress this one enough. I don't care how smart you are, if you are an asshole, your career is not gonna work out.
Try really hard not to be negative, even when there is reason to be. Try not to be openly negative about the company or a particular employee. It's poison for you and your teammates and makes you feel worse.
Don't get defensive when someone makes suggestions to your code (I still battle this).
Don't base your self worth by other people's compliments. They're nice, but the company complements you every time they cut you a check.
When someone does compliment you, the best reaction is a simple, "Thanks!"
The people you work with are called colleagues, not friends. Sometimes it can hop over, but don't divulge personal information to a colleague that should only be shared amongst friends.
Keep your behavior professional, even if the company's culture isn't so much. Also, never get drunk at company parties.