1. Never have an office romance. Don't even think about anyone you work with in that way.
2. Never gossip.
3. Treat all of your colleagues, whether above or below you, with respect at all times.
4. Set clear boundaries between your office life and your personal life. Hanging out with your coworkers doesn't mean they're your personal friends. Usually socializing after hours is just for team building or networking.
5. Small talk is a learnable and essential skill. The key to making small talk is to make a person feel like you're having a light personal conversation, when it's in fact very generic and not personal at all.
6. Leave your personal issues at home. If one day you're unable to do this, call in sick for that day. However, if you find yourself calling in sick too often, you may need to re-evaluate your situation and possibly make some major changes. Only at this point, and only if there is some accommodation at work that could alleviate your problem, you should raise the situation with your manager in the most professional manner possible.
7. Never say anything at work that you wouldn't want written, and never write anything that you wouldn't want your grandmother to read.
8. Never argue.
9. Make mental notes about when a person doesn't want to be disturbed, and don't disturb them at these times.
10. Don't ask personal questions directly. Don't put anyone on the spot, especially on skill-based technical issues. Don't talk about your personal health (physical or mental). etc. You get the picture.