let the vehicle get to operating temperature(very, very, i can't stress this enough important) > watch something like a plug wire that is vibrating > turn distributor to the point where the wire is moving the least(engine running smoothest) > tighten bolt > kill engine > restart immediately > if the engine has a hard time turning over(like the starter is having a hard time moving it) retard the timing a little...if not, it's set > hit the balancer with a timing light so you know the timing for future reference.
hope that helps