Remove #1 plug, put your finger over the hole and bump the motor over until you feel the compression push your finger away. Stop there and look for the timing marks on the balancer. Be sure you have the timing tab installed first. Then either bump the starter or move it with a breaker bar to line up the "O" to the timing tab pointer. Wherever #1 is on your dist. cap, mark a line on the housing of the distributor. Drop the distributor in with the rotor pointing toward the mark on the housing. If it doesn't drop all the way down, keep pressure on the distributor housing and bump the starter over to engage the oil pump shaft.
Sounds simple, huh?
The other way is if you have the valve covers off. Bump the motor over and watch the intake valve. When it goes down and comes back up, watch for the timing marks on the balancer to come up. Then do the rest of the above.