There are a couple different styles available. There are some that are pretty expensive, built more for shop use, and some that are lighter-duty, perfect for your personal garage. They go for around $90.00, much less expensive than experimenting with wheels and tires. The tool bolts to your hub and has an arm that is adjustable, mimicking the space the tire would take up. You can figure tire width, tire height, and wheel backspacing. In the front, be sure to turn the wheel lock to lock, and compensate for body roll and braking forces.
Another way to find out what might fit, is to do some research on what has been done before. Internet forums are a great resource, as they serve as an every-day meeting place for people who want to talk to you about their cars. A simple post asking what fits would yield pages of responses on a popular site like pro-touring.com for example. Keeping an eye out at car shows for wheel/tire combos can help as well.
Percy's tire sizing tool at Summit Racing