I just did two cars and both are working well, but, I know relatively little about AC, so take this for what it's worth.
Compressor spinning, you will have a low and high side reading. You really want to to have both. (or I do at least)
Compressor off, the high side will drop and the low side will rise until they equalize, sp yes, the low side pressure will actually rise when the compressor is off.
I used a chart like this, and am totally open to tips from people who know more.
Yo' Bob, how frequent is frequent?
(I've got one car that blows ice cold, but cycles a lot. If anything, I'm scared I overfilled it)
edit- both cars I did from empty vacuum, and tried to add refrigerant by weight, but ended up needing more than what I thought (weightwise), lost track of weight, so I just used "the force" and went by closest approximation of pressures.