For verbal, my preparation has been concentrated, so far, on SC and CR. The texts that I'm using are the Manhattan SC and Powerscore CR, and I'm happy with both of them.
For sentence correction, it was pretty obvious what would be taught - grammar and good English use. For critical reasoning, I've been impressed with how the task is broken down, eg. identifying the premises and the conclusion(s).
For reading comprehension, I'm not yet sure what the study texts teach. I have done some research, but I haven't been able to work out:
* What do the various RC resources teach, specifically?
* What broad approaches to RC are there? Eg. taking detailed/sparse notes, drawing pretty pictures or diagrams, not writing notes at all? Looking for specific markers, finding the important sections, or learning to disregard red-herrings?
* Which resources use which approaches? (eg. Veritas, Kaplan, Manhattan etc)