In a perfect world, you'd succeed (or fail) at your career based solely on merit. Perhaps you can in a few isolated places, but in most offices, you need to know how to play the office politics game. And things don't improve as you climb up the career ladder. In fact, as you move up, you're likely to find yourself threatened from every direction: from above (your bosses), from below (your staff) and from the side (your peers). Here are some tips on understanding each kind of adversary and ways to cover your flanks:

Your staff: Though it might seem foolhardy for one of your direct reports to challenge you, it happens all the time. The reason is simple enough: as your staff members see it, you're the only thing standing in the way of their career advancement. If indeed one of your staff members is maneuvering for your job, you'll need to be on your guard at all times. He (or she) will likely be lying in wait for you to make a mistake so he (or she) can capitalize on that error.

The best defense: Your best defensive move is to keep a cool head and careful notes. If one of your staffers challenges you in a public setting (like a meeting), don't rise to the bait. Listen carefully to everything that's said and respond professionally, not emotionally. Don't sink to his or her level. You want to avoid doing or saying anything that might prompt your workforce to take sides.

If you meet privately with this staff member, document everything. Make notes on the meeting as soon as it's over. Note the time and date on each document. All of this paper will come in handy if you need to fire this individual or defend your actions to your supervisors.

Your peers: We all like to think of our co-workers as friends, but sometimes one of those co-workers will try to undermine you. The root cause is almost always that person's competitive nature—whether he's trying to beat you out for a promotion or simply outperform you. You should be aware that the more cold-blooded among them will have no qualms about attempting to worm your ideas or opinions out of you so they can use them against you or take credit for them.

The best defense: The best defensive maneuver is to watch what you say. Never tell anyone with a connection to the company something you wouldn't want your boss to hear. Always maintain a professional demeanor and refrain from discussing your personal life in the office. If you want to run ideas by your co-workers, do it by e-mail and save a copy of the message, which will document the time, date and source.

Your bosses: You'd think your boss would be that last person who would want to sabotage you, but unfortunately it's all too common. The cause is usually an insecure boss who perceives your accomplishments as efforts to make him (or her) look bad by comparison. The harder you try to prove yourself to these bosses, the more convinced they are that you're after their job.

The best defense: Guard against bragging about your accomplishments at work, especially to your supervisor. With this kind of boss, the safest approach is to do exactly what you're asked to do and do it as well as you can. If you earn, say, a master's degree or a national certification, notify human resources so that they can update your employee file. But otherwise, keep quiet. You want to stay under your boss's radar until such time as you decide to make a move of your own.