Smart thinking. It's always best to know what you'll be able to qualify for before you start shopping for the car.
If you belong to a credit union, that should be your first stop. If your not a credit union member you can still get a loan from them, but you'll probably be required to open a checking or savings account with them. The minimum balance is usually very low.
Another good place to check would be your bank. Any bank would do, but the best choice is a bank where you're an established customer.
You could take out a home equity loan or use a home equity line of credit. If your buying a used car, this probably is not the best bet.
The dealership where you buy the car can also help you with financing. Once again this is not your best option. Their rates are usually higher, and personally I find them difficult to deal with.
Good luck.