There are different ways to go about testing all your lifts. Usually you want to do it at the end of a program/cycle. You can have a test week where you test all your lifts within one training week (i.e. Monday - BS, Thursday - Snatch/C&J, Saturday - FS). There have also been instances where people have tested Snatch/C&J/BS or FS in the same training session.
For a beginner, I feel like they should go through a beginner program that focuses more on technique and posture to get the body moving correctly. Then, to finish up that program, they can go for a 1 rep max to set them up for a more advanced program that works off of percentages. But during that beginner program, I think they should work off of how they feel rather than percentages.
As for the day of testing, there's not really any "strategy." Just go into the training session as if it's any other day and lift heavy.