1- Your turn signals are there for a reason. Use them, but only when you're getting ready to make a turn! Now, I admit that I have forgotten to turn off a turn signal after changing lanes, but it doesn't happen often, and at least I was using the damned thing!
2- Also, it is a good idea to pay attention to the people who are driving around you. You're not the only person on the road, and the other drivers' predictive capabilities may be hampered by the momentary glance in the rear-view mirror or something, so don't suddenly decide to pull of to the right side of the road and then, even more suddenly and with even less warning, make a u-turn across the path of the people behind you. It's great that you were aware of the absence of on-coming traffic in the other lane, but some awareness of the people behind you would be good too.
This morning on the way to Rachel's school, some moron in a mini-van pulled out of traffic to the right as if to park, without signalling. OK, fine - would have been nice if you'd signalled, but you're not in the way, so it's not that big a ... WHOA!!!
I managed to yell only "make up your mind" in front of Rachel, rather than the various more colorful things that went through my mind, such as "what the fuck are you doing, you stupid fucking idiot bitch!??!"
And then there was the guy Dawn was telling me about who, in a large pickup, came racing up behind her on the freeway, honked, and then raced around her. She called him an asshole. And the guy who came up behind me on the frontage road on the way to work, where the limit is 35 and I was doing 40, and then crossed the double yellow line to pass me.
I tell ya. It's far too easy to get a license, not to mention a car, in this state (and probably country). The number of people who either haven't had any real driver training or are completely incapable of following any semblance of the rules is ridiculous.
I'm just sayin' :-)