Agreed with balance. For me personally, I felt that practicing reading comprehension was a waste of time so long as I had a method for it. I only did a few practice tests in order to learn how to most effectively map the passage. If you can learn to number each paragraph (numbers are given to you on the test, so it's easy to backtrack) and jot down a couple of very, very brief descriptions to make it easy to jog your memory and find, you should do well. I hardly practiced the section at all and still managed to get a high score; at times I felt like the questions went in order with the passage, though, so maybe I just got an easy RC test.
Bottom line, though, is to use a mapping method that works for you, and to practice doing that when you read.