Learn who you are.
People matter, even if you're an introvert. Make friends. Don't be a jerk to people.
How you dress matters, even if you think it doesn't (or shouldn't). You don't have to "dress to impress", but don't look like a slob.
Develop empathy. Don't be so focused on getting your code to work, or your hobbies, or whatever, that you don't notice when people are in pain.