Study Plan to Improve CR

Dear All, Im facing some trouble with CR. It´s been 1,5 half that Im studying for Gmat and I´have already done many questions (including Official guide and Kaplan)of all types of CR, but I´m still making many mistakes: whether Im sure about the answer or I have no idea about what answer should be. To make it worse, it´s not that Im stuck with one type of question; it really depends on the question itself.

Do you have any tip or recommendation to improve my score in CR?

Thanks a lot
Regards
Thabata