This is what my friend who went from a 510-670 in 31 days:
ok here are the steps:
1- get ritilan from your doctor
2- get the exact dry erase board you will use in the test and the markers
3- go to manhattan gmat
.com and use their stop watch. Give yourself 10 minutes and do 5 questions from the official guide. If you get the question wrong go back in 3 days and do it again. Even if it was a careless mistake. Do every question in the 11th edition and quant, maybe verbal too.
4- If there is a category of questions you are particularly weak in go to the manhattan gmat
book for that category and understand why you are getting them wrong.
5- review each question you got wrong and understand.
6- lock yourself away for the next 30 days, do not go out, do not talk to people and dedicate your life to getting the score you want so you can get into the school you want so you can have the life you want. It is not fun but there really isn't any other way.