Often in my experience the biggest problem with Verbal scores is failing to understand the relationship between the questions and the answers properly.
The easiest place to do this is to find a good Sentence Correction review. I've written my own for clients (PM me if you're interested), but many out there are reasonable in terms of content--however, they have a tendency to read like hifi instructions. Finding one that has good examples and is written in a conversational-enough style to make sense will do wonders.
However, remember that Sentence Correction is designed to be spectacularly confusing and while you can raise your score quickly, it is difficult to get every question right.
For Critical Reasoning, outlining the logic of the problem much like you would do for the Argument Essay is very helpful. Next, look at the answer choices and eliminate the choices that are "out of scope."
That is, if you are talking about a particular Mangrove tree in a particular swamp in Florida, your answer will deal with that particular tree in that particular swamp in Florida, and you can eliminate answers dealing with, say, a branch on that tree (scope too narrow) or Florida in general (too broad).
For Reading Comprehension, remember that the testwriters are subjective in their answer choices. That is, who knows what they're smoking behind closed doors. However, "subjective" doesn't mean "arbitrary." THERE IS A SYSTEM TO HOW THEY CHOOSE ANSWERS, and it takes a little bit of concerted effort to learn it.
The best thing to do is to take answers you are not 100% sure of and write justifications (3-4 sentences in length, usually) for each of the answers, specifically highlighting how it is superior to the original answer you chose.
With a little bit of sweating over that, you will "miraculously" begin to see how the testwriters think when they pick one answer over another.
Good luck!