Is there an easy way to set motor timing?

[JSN]

So... I'm starting to fool with different arm and can combos... so far things are working out fine other than I don't know a good way to find Zero timing. What I have done so far it set timing by ear so the motor spins the same speed or as close as my ear can get it in both forward and reverse then play with advancing/retarding from that point... is there a better more accurate way to find Zero?