Useful friends

Not to sound too Machiavellian but friendships can be useful in advancing one's interests.
In an office, there are many people whose friendships can be quite useful. I don't mean to condone to befriend people on false pretenses, but it never hurts to make certain that you are friendly with people who can help you.
If that is harsh, please consider this my list of people with whom you should especially avoid making enemies.

1. Administrative staff(secretaries and assistants), you want to know who knows about an upcoming layoff or big contract, the administrators. They handle their managers documents, their emails, they plan their trips, they know almost as much as their managers. They may also carry some influence with their managers. You should never make an enemy out of an admin, and it doesn't hurt to chat with them from time to time.
2. IT Administrators, same type of deal with the assistants. System administrators can really help you out if you are in a bind. Having a friend who can get your computer repaired or give you an off the record ETA on an issue is a big help.
3. HR, you want to know what's going on in your company, make really good friends with HR. They know everything. If you get on their good side your life will be a lot easier than if you are in an adversarial relationship.
4. Managers, even if they aren't yours you should be nice to managers. Consider them your safety valves. If your current situation isn't working out, they may be able to facilitate a transfer to their group.
5. Outgoing people, don't think of someone's leaving the office as abandoning you. Think of it as opening a door to possible opportunities. There's no telling what's going to happen at your office. Your company may be acquired, the brass may decide to outsource the whole division to India, they may make working there unenjoyable. Having friends outside the company who can help you is a great asset.
   

Our culture has a negative perception of people who use others. It isn't necessarily a bad thing. Don't feel guilty for looking at how people can help you. If helping others is something that you enjoy doing, you probably look for opportunities that you can help others. When you ask people for help you give them the opportunity to feel good about helping you.