Combination Discounts
You can often knock off 10% to 20% from your premiums if you insure both your home and your car with the same company, or by insuring more than one car with the same company.

Defensive-Driving Classes
This can often merit a 10% discount on premiums.

Good-Student Discounts
Students with GPAs of 3.0 or higher can be eligible for discounts of as much as 25%. In some cases, young male drivers may benefit from this more, since their premiums are typically higher, says Dick Luedke, a State Farm spokesman.

Retirement Discounts
Be sure to let your insurer know when you retire — particularly if you retire at a relatively young age. Since you're likely to be driving less once you're working days are over, this can often earn you a break on premiums.

Association & Group Discounts
Discounts may be available for affiliation with all sorts of associations — your alma matter, a military group, a professional organization, even Mensa. If you work for a large employer, that could earn you a discount as well.

College-Kids-Who-Are-Far-Away Discounts
If at least 100 miles separate your kid from your car, you could save up to 40%.

Safety Discounts
This varies by state. In some states, including New York and Florida, drivers must be rewarded for having certain safety features on their car, such as antilock brakes, airbags and automatic seat belts. Certain antitheft devices could be eligible for a discount as well.

Loyalty Discounts
Stick with the same company for more than one year, and you could earn a break of 10% or more on your premiums.