1. Read this: http://www.luminous-landscape.com/reviews/accessories/eye_one_pro_ii.shtml
You’ll get an idea about what M standard is trying to do. If you are unsure, measure using M1+M2, build a profile both ways, see what you prefer under the illuminant you’ll view the prints which has an effect.
2. Pick D50 UNLESS you are aiming for a specific illuminate (say you are printing a gallery show). Take the i1Pro-2 there, take a reading, build the profile with that exact reading.
3. IF you have a boat load of OAB’s, you’ll run this process and visually view the target under the illuminant and dial in a number that will affect the iteration of the original profile or data. The gray’s are on the Macbeth Holy checker you should have received with the package.