Primary coverage is the insurance on the car, not on the driver. So if you’re using someone else’s car, their insurance is the first one that will be used in the event of an accident. The driver’s insurance may be used for secondary coverage.
For rental cars, your insurance policy typically covers up to 21 days use of a car rented for personal use (not business purposes), but only in the United States and Canada. However, the primary insurance for liability is provided by the rental car company; your insurance policy is typically used only for comprehensive and collision coverage. Thus the extra, optional charges you may get when you rent a car mainly cover the cost of your deductible for these coverages. Secondary coverage is also provided when you charge your rental to a premium credit card (American Express, Gold MasterCard, Gold Visa) but is often only valid if you notify the credit card company within 48 hours of the accident, so don’t forget to do this. When renting a car outside of North America, it’s often a good idea to purchase optional coverage since these secondary coverages are often not valid there.
The longer you carry coverage with your insurance company, the bigger a discount they will give you on your premiums, and the more forgiving they will be (e.g. not increasing your premiums for your first accident).
When determining the premium when writing a new policy, they look at how many accidents and tickets you have had in the previous three years, and how many major accidents and tickets (e.g. DUI) in the previous five years. For premiums on renewing a policy, tickets don’t have any effect on your premiums, only accidents in the previous three years. However, if you lose your license, your policy is revoked so it does affect you.
All insurance claims are filed through a central bureau (Equifax) so if you’re shopping around for insurance, the insurance companies will be aware of any previous claims. They might not know that a claim was for a track event but they will know the amount paid on the claim.
If you incur damage from hitting a pothole or debris on the street and you file a claim, it is considered a chargeable accident. If you incur damage from airborne debris or from hitting an animal, it is considered covered under the comprehensive portion of your insurance. If you have an accident but your insurance company doesn’t pay anything (either you pay for it yourself or another insurance company pays), it is classified as “settled without payment”, which means it doesn’t count against you in determining your driving record.
The average person files an auto insurance claim once every eight to nine years.
The factors that determine your insurance rates are: (1) your driving record, including tickets and accidents (2) your age (3) the location where your car is garaged (or normally kept) (4) the year, make, and model of your car (5) how your car is used, and (6) what coverages you get for your car. As a multiple of the premium paid by a middle-aged person, a teenage male occasional driver pays 2.75 times as much, a teenage male primary driver pays 3.85 times as much, a teenage male primary driver with a good student discount (B average or better) pays 2.90 times as much, a teenage female occasional driver pays 1.85 times as much, a teenage female primary driver pays 2.35 times as much, a teenage female primary driver with a good student discount (B average or better) pays 1.75 times as much. Thus it costs less to include a teenage family member as an occasional driver on the family’s policy than as a primary driver on his/her own policy; however, if he/she has his/her own car, he is automatically considered the primary driver. This is the case whenever the number of cars mandates it - for example, if you have two adults and a teenager, and are insuring three cars, the teenager is automatically considered a primary driver. Unfortunately, this is likely to be applied to NSX owners for whom the NSX is not their daily driver but a second or third car, even if the teenager really IS only an occasional driver.

from the evo boards:

I’m a claim adjuster with one of the big auto ins companies…I won’t say who though. Anyways, if you look at your policy doc it’ll definitely fall under comp (missle, projected obj). With your ins history (no claims within the last few years) it shouldn’t affect your premium at all. Especially for something that was at “no-fault”. In this particular case, it would be a no brainer to make a claim under comprehensive. Comp is good.

Likewise, you may not have to take out insurance on the rental car from the rental company because many credit card companies, including Visa and MasterCard, automatically offer this insurance if you pay for the car rental using one or other of the cards. Of course, you need to check with your credit card provider about the coverage, and if you do find that such coverage is on offer, you effectively don’t have to take out a separate rental car insurance at all, because your own auto insurance covers liability, and your credit card covers the rental car.

link to masterrental coverage