When applying something to the face between phases, how do you know it's time to move to the next? In other words, when lathering up, how long should it set before taking the razor to it? How long should pre-shave oil set? A/S before ASB or ASL?
the procedure is different for each phase, but in general you should go in order as soon as you are comfortable. I don't like to feel rushed but some people like to speed shave. I skip the Pre shave oil. For lather, I face lather so it sits for a full minute or so before I bring blade to skin. Then after final pass I do a warm/cold rinse and splash on some alcohol aftershave.
Sanuginz covered my opinion on the lather (a full minute before the hot towel or the blade) so I'll mention my preshave oil prep.
Personally, I apply the PSO right out of the shower when my skin is still damp. I let it sink in while I gel my hair and make my lather - about 5-10 minutes. Its usually good to go for lathering after that.
I go at least two minutes for prep, regardless of whether it's just hot water, or a hot towel, or just going straight to the lather. I try not to wait at all between passes, and even relather part of my face right away to keep the beard wet all the time until the shave's complete. I don't use preshave oil, so I can't comment there. For after shaves, I go back and forth, sometimes using alcohol or balm AS wet, sometimes dry. I do let one type of AS dry off before putting another kind on, or at least rinse--I might do alcohol then rinse and add witch hazel w9thout drying if I think I need it after that.