want a strategy for preparing GMAT, my goal is just >600

Want to know a strategy for preparing GMAT. I have 28 days to prepare part-timely and need a score more than 600.

Anybody give me any suggestion for preparing it? And how to handle every question during the test?

Do I have to complete each question during the test, because I am not sure if I could complete the reading section.

Thank you very much in advance.

http://forum.chasedream.com/dispbbs.asp?boardID=34&ID=1092&page=1

里面有不少PART-TIME的经验。