Colleagues should be treated with respect. Make all your colleagues feel equally valued and, if you are in a position of seniority, don't single people out for either excessive criticism or praise.
Not all topics of conversation are suitable for office chitchat, especially in an open plan environment. Don't embarrass your colleagues by discussing inappropriate or personal topics and resist the temptation to gossip about other members of staff.
Try to keep your work life and private life separate as much as possible and this includes limiting your personal calls. However, it is important to open up a little and find some common ground with your colleagues.
Support your workmates and they will do the same for you in your hour of need. If you can see someone is particularly busy or stressed there may be some way you can help without affecting your own workload too much.
Always credit colleagues where it's deserved; never steal ideas or take credit for something that wasn't your idea.
Be willing to dedicate time and effort to your relationships with colleagues. This may mean giving up an evening for some after work drinks or going out for lunch together once in a while.
However petty, juvenile or ruthless your colleagues may seem, remind yourself that they are human beings with lives outside the office. Treat all colleagues with courtesy, irrespective of hierarchy.