When I'm 'shepherding' books through the manufacturing process, I first check their proofs for compliance with the ISO standard by insisting that they make me a proof of the Idealliance proofing bar. I check it with my EyeOne. I like to see the proof as close as possible to a Delta E of 1.0. If they are making good proofs, we're half-way home!. I then have them proof the job and send it to my client for his approval.
After the bar looks good on the presssheet, we can start fine-tuning the images, but typically there is very little adjustment that needs to be made to match the proof.