Remove the cap from the distributor. Rotate the engine until the distributor rotor points to either #1 or #4 position and points begin to open. Then you should see the 0 mark on the timing cover line up with the single mark on the crankshaft pully.

With the A-series engine, you can turn the engine clockwise or anti-clockwise. So it is safe to turn it back a little, then forward again.