I was promoted to lead a group of peers at work years ago.

Take a one-day "How to Supervise People" seminar, even if it has to be at your own expense. This is one that I like: http://www.careertrack.com/mkt_info/seminars/desc/TW.asp .

Listen to your people. Ask them for their suggestions. Then make your decision.

Praise in public, criticize in private. Criticism should be constructive whenever possible.

When something goes wrong, accept the blame. Their failures are your failures. When something goes right, give credit to the subordinate. Their successes are your successes.

Communicate clearly, and frequently. A very common source of employee discontent is a lack of feedback.

Fight to make sure your people have what they need to get the job done. Shield them from upper management foolishness.

Do not lie to your people, ever. Keep faith with them and the good ones will keep faith with you.

Don't be afraid to delegate, and don't be afraid to pitch in.

When I brought a new person on board, I gave them a little speech: "If you see me about to do something stupid, stop me. Part of your job is to keep me from stepping on my dick. I hired you for your brains, not your hands."