Having taught the MSF course for many years and riding a motorcycle for 42 years and who knows how many miles, I can tell you this, I never stop learning and trying to improve my skills and abilities. In addition to all the great information I've seen here, I'd like to add:
1. Know your riding abilities and ride within them. (Practice, practice, practice) Not everyone's abilities are the same, do not try to ride like anyone but yourself.
2. Be a defensive driver. Ride like you're invisible to other drivers. (Chances are, you are) Unlike European drivers who are used to seeing bicycles on the roads, Americans are not "conditioned" to register motorcycles or bicycles in their minds, hence the common statement after an accident, "I didn't see the motorcycle".
3. Conspicuity - be seen. Anything you can wear (reflective clothing/vest if you ride at night a lot); I know I'll get flamed for this, but leave your reflectors on the side of your bike; this is one of the only means of being seen at night from a perpendicular angle to a car's headlights. Adding brighter, and more, lights to the front and rear help, along with modulators, etc. Anything to gain the attention (especially at night) of other drivers.
4. When riding with your BSR, one of the most important things you can tell them is when you are leaning into a corner, for them to look over your corresponding shoulder. In other words, if you're leaning right, have them look over your right shoulder. This immediately puts them into leaning with the bike and not trying to do the leaning out of the turn manuever (like you would on a snowmobile).
5. Alcohol and riding. If you're going to start drinking, stop driving. So if you plan to stop to have that "one" beer or drink, seriously consider having that at the end of your ride/day. Motorcyle riding requires all of your senses be unimpaired. I don't care how good of a drinker or rider you may consider yourself, drinking and riding do not mix.
6. Remember the rule of masses. "He who has the most mass, rules." You're riding a motorcycle, in a battle between you and a car, truck, semi, they have the greater mass and you will lose. Do not test that theory, give yourself a route of escape, and yield to them. Try to anticipate what the driver is going to do. You'll find out that you're going to be right about 80% of the time.