If it's related to ignorance towards alcohol, then perhaps a suggestion could be compulsory drink driving simulations. That way, the youth makes the error without costing any lives. Another alternative would be complulsory attendance to lecturers, where a relative of a car crash victim, or former drink driver speaks of their experience/s. There could also be a graphic cinema of a car accident.
Neither of those will do much good, I'm afraid. I'm not so far out of my high school years that I don't remember some of the caustic and stupid remarks we made about the guy with the sad story because his kid was killed because someone DUI'd. It's not cool to drive safely and I think that, in the case of teens, it just takes a close call or a tragedy. It's sad, but my own experience tells me that's the case. Of course, more strenuous examinations and graduated licenses are important steps.
More experience with an adult is going to provide someone with experience if the unfortunate does happen and will help make good driving behavior an actual habit. Teenagers will do what they're supposed to when there's an adult, but when backs are turned... Well, we were (or are) all teenagers once, right? Practice does make perfect. Take my head lamps. I don't need them during the day, but I'm so programmed to turn them on from driving at night so much that I turn them on everytime I start the car.
As far as graduated licenses, reducing the opportunities for teenagers to get into accidents is really a common sense kind of thing. Accidents are more likely to happen at night because it's dark and because of the sorts of activities that occur at night. If a kid can't drive home at night after the party because of a license restriction, there's less chance they'll drive home drunk. At least in my state, being suspected of violating your license b/c of your age is probable cause to be pulled over. So, there's that.
Something else, too, that I don't think anyone really discusses is who can drive certain classes of vehicles. To be honestly, teenagers don't need giant yacht-sized SUVs or sports cars. Both of those vehicles foster the kind of habits that can cause accidents. Even restrictions on certain modifications should be considered. There's a guy that buys parts from that put 24" wheels on a Charger. He can't turn the vehicle properly, which isn't safe and should be illegal.
While it's only tangentially related, the OP did mention it: The elderly. No, their licenses shouldn't be taken, per se, but more frequent tests of things like visual acuity and reflexes are needed. Especially when they insist on buying cars with features they don't understand. One thing that should also be looked at (not just seniors, mind you) ties back into my previous point: The kind of vehicle. Yeah, you can drive a car, but can you drive this car? I can't tell you how many people I've seen that are used to automatics decide to switch to manual and chaos ensues. Not too long ago, in fact, a woman drove her car into a store front near where I work because she just bought the car and didn't realize how loose auto-stick can be. She slipped it past reverse and right into a towing gear. I like to think I'm a good driver, but the first time I used a car with that, something similar happened.
The question, then, is who pays for the testing? Maybe it could be factored into the license. I'd gladly pay more in licensing fees to have safer roads. Anyone who wouldn't is either selfish or foolish. A price cannot be put upon safety.