One obvious thing to point out is that safety features (airbags, anti-lock brakes, etc) do positively affect premiums, so that’s a good place to start.  Those ‘peace of mind’ features are also good for your car insurance rates. Any vehicle that is marketed as supercharged or is considered by the industry to be a “hot” car is going to drive premium in the wrong direction. Sports cars come to mind, but midsize cars with supercharged engines or luxury cars with some high end options can also trigger this surcharge and add to the cost.  Lastly, there is the issue of comprehensive and collision coverage (commonly referred to as “full coverage”).  If the car is new enough to have modern safety features, but not so expensive that you can’t afford to have liability only- then putting your younger driver in a car with liability only will significantly reduce the premium, maybe by as much as $1k/year or more.  If the car does need to have full coverage- then the more expensive the car...the more expensive the insurance. All of these things are true of all insurance policies...but every price difference is multiplied when it involves an inexperienced driver.
One more tip that may not be practical for every situation- but will definitely reduce the cost, is to have more drivers than cars.  In other words, if Johnny has a license- but not his own car, your rates will not go up nearly as much.  It isn't enough to tell your agent or insurance company that the car isn't "his".  If there are 3 drivers, and there are 3 or more cars, the insurance company system assumes that your teenager is the primary driver of at least one of them, regardless of how vehemently you try to convince them otherwise.  The only way to reduce the young driver usage to 'part time' or 'secondary' is to have fewer vehicles than drivers.