I almost always do -0 or -1, but I barely mark anything. I stop at the end of every paragraph and make sure I understand what it's saying and how it relates to what came before, and I may make a very brief note in the margin (two or three words) noting what function that paragraph is serving. And if the passage states something like "There are two main reasons for this." I'll underline the indicators for the two reasons (e.g., "First of all," or "The second reason is") so I can find them again quickly. Otherwise, I find that thinking about what to mark up takes time away from thinking about what the passage is saying.

The guided meditations here: http://marc.ucla.edu/body.cfm?id=22 and the "Guided Meditation on the Breath" here: http://www.audiodharma.org/series/1/talk/1835/ are good starting points for meditation. Headspace.com also has a good 10-part intro to meditation. Totally recommend it.