It’s a good idea to turn on your headlights when it’s raining enough that you want to use your windshield wipers. It won’t help you see, but it will help other drivers see you (which is just as important). It’s the law in some states, but it’s a good idea everywhere.
If you leave a huge amount of space in front of your car, more than most other drivers are leaving in front of themselves, don’t be surprised when people merge into it.
Don’t ride with your foot on the brakes, tapping the brakes periodically, unless there really is no other option. It wears out your brakes and annoys the person behind you. I actually did learn this one in driver’s ed, as well as that brake-tapping is often the result of driving with one foot on the brakes and one on the gas, and that’s why you shouldn’t use your feet that way while driving.
Driving when you’re really tired is a bad idea.
Unless you are in a police car, it is not your job to make sure that other drivers obey the rules of the road. Nor are you the road mod- it’s not your job to punish other drivers for being jerks. You’re not a driving instructor, either- it’s not your job to teach another driver a lesson.
In the spirit of those rules, don’t go the speed limit in the far left lane, or try to keep people from passing you when you are going the speed limit. It’s not your job to enforce the speed limit.
You don’t want to annoy other drivers, no matter who they are or what they do. People’s driving generally doesn’t improve when they are annoyed.
Driving near somebody who’s driving unpredictably or driving like a jerk is generally a no-win situation. If you see someone driving like that, you should try to get as far away from them as you can. If they’re driving like they’re drunk, call the cops on them by all means. But after you do, get away from them. It might be interesting to see the cops pull them over, but it’s very dangerous to drive near a drunk or otherwise unpredictable driver.