The Schacht manual has good info on where to oil.
My tendency is to oil the flyer rod each time I change a bobbin. Keeps the wheel quiet. Also if the wheel has been sitting for a while, I'll oil around the footman (vertical bar attached to the footpedals), it tends to get squeaky first.
Those are the only two places a Schacht wheel is supposed to be oiled, according to their manual.
(posted by me on spinning_camp, 3/5/2007)
((that's a really old picture of me, when I first got my Schacht...))