I line edit the first hundred pages; after that you should be able to follow what's gone before.
I jot notes on the mss. pages, both pro and con.
After reading the entire mss., I consider many points, among them writing ability, pace, characterization, plot, etc. and suggest ways that the writer can improve upon what's already on the page (if, indeed they can).
Each mss. is returned with a full set of notes that addresses any changes I feel need to be made.
If the writer wishes me to reread the mss. after it's been reworked and prior to submission, there is no charge for the secondary consultation.