I feel like for critical reading and reading comprehension there's really nothing else one can do except to read everything very very carefully and then do practice problems. This is unlike other sections of the GMAT where there is "content" to be mastered.
Also, if it's a "seriously weaken" question, try to imagine that someone who(m) annoys you/you detest is making the claim (Lord Voldemort? :twisted: ). I don't use this, but it has worked for quite a few people on these forums.
