Under 25 yr old male + sports car = reamed in the ass for car insurance, just a fact of life.
The best ways to get the cheapest insurance for you are:
1) Do not buy a sports car, get something like a Honda Civic LX 4 door, airbags, ABS if you can, install a car alarm -or- buy a sports car and pay like $100-$200 more per month, your choice.
2) Make sure that you live with your parents and try to get on their auto/home insurance policy.
3) Take drivers ed at school.
4) Maintain at least a 3.5 GPA.
5) I'm not sure if this last part is worth it or not, but go to a driving school like Sears driving school. May lower your premiums.
6) When comparison shopping for car insurance check out
American Express they have some pretty incredible deals.