After making sure that the center of the chassis was square, I put the frame rails on blocks and then measured with a level to make sure the front clip was level side to side and front to back. Also check the shock tower to the firewall and make sure they are equal. Sting the side of the car to make sure the front clip is pointed forward. A jig is always better if you have access, but this is how I did mine to get it back to stock.
All of this is assuming that there are not any intentional tweaks like Gimpster is talking about. I do not have the experience to mess with moving things, so I would probably just make the car worse if I start messing with the clip. If the car you buy was done by a particular builder, you might want to call and ask for some baseline measurements so you can adjust it back after contact.