Update [07/01]: you can now order a copy of Swanson's Unwritten Rules of Management.

Bill Swanson, CEO of Raytheon, offers this list:

Learn to say, "I don't know." If used when appropriate, it will be often. It is easier to get into something than it is to get out of it. If you are not criticized, you may not be doing much. Look for what is missing. Many know how to improve what's there, but few can see what isn't there. Viewgraph rule: When something appears on a viewgraph (an overhead transparency), assume the world knows about it, and deal with it accordingly. Work for a boss with whom you are comfortable telling it like it is. Remember that you can't pick your relatives, but you can pick your boss. Constantly review developments to make sure that the actual benefits are what they are supposed to be. Avoid Newton's Law. However menial and trivial your early assignments may appear, give them your best efforts. Persistence or tenacity is the disposition to persevere in spite of difficulties, discouragement, or indifference. Don't be known as a good starter but a poor finisher. In completing a project, don't wait for others; go after them, and make sure it gets done. Confirm your instructions and the commitments of others in writing. Don't assume it will get done! Don't be timid; speak up. Express yourself, and promote your ideas. Practice shows that those who speak the most knowingly and confidently often end up with the assignment to get it done. Strive for brevity and clarity in oral and written reports. Be extremely careful of the accuracy of your statements. Don't overlook the fact that you are working for a boss.

* Keep him or her informed. Avoid surprises!

* Whatever the boss wants takes top priority. Promises, schedules, and estimates are important instruments in a well-ordered business.

* You must make promises. Don't lean on the often-used phrase, "I can't estimate it because it depends upon many uncertain factors." Never direct a complaint to the top. A serious offense is to "cc" a person's boss. When dealing with outsiders, remember that you represent the company. Be careful of your commitments. Cultivate the habit of "boiling matters down" to the simplest terms. An elevator speech is the best way. Don't get excited in engineering emergencies. Keep your feet on the ground. Cultivate the habit of making quick, clean-cut decisions. When making decisions, the pros are much easier to deal with than the cons. Your boss wants to see the cons also. Don't ever lose your sense of humor. Have fun at what you do. It will reflect in your work. No one likes a grump except another grump.

Taken from here (also, recently mentioned in Business 2.0 magazine as referenced by Tom Peter's very useful TP Wire Service). The Business 2.0 article requires a subscription, but includes an explanatory comment from Swanson on each one. It also omits some rules from the list above, while adding others.

Update (06/27) - this post is getting a lot of traffic today, so I thought I would add the "extra" rules from the Business 2.0 article (the parentheticals are mine).

You can't polish a sneaker. (notice when something hasn't got any real substance) You remember 1/3 of what you read, 1/2 of what people tell you, but 100 percent of what you feel. (leaders generate emotions that move people in the desired direction) Treat your company name as if it were your own (possibly the same as #19 above) When faced with decisions, try to look at them as if you were one level up in the organization. Your perspective will change quickly. (your boss has to weigh more considerations than you do in making a decision) A person who is nice to you but rude to the watiter is not a nice person. When facing issues or problems that are becoming drawn out, "short them to ground." (solve problems instead of talking about solving problems).

Lists like these are reassuring. But the real trick is to put them into practice when you're in the thick of the fray. What ever your rule set, it's application has to be internalized and almost reflexive to be effective.