Work on the
MGMAT books, together with the OG, solving every problem from the OG the
MGMAT books tell you to WHEN they tell you to, careful not to proceed further without understanding the concept and being able to execute quickly.
Work on the
MGMAT online tests and CATs, dissecting every problem.
Work through the problems here, on GMATClub, timing them and logging the results in your workbook, revising every error or every question which took too long to solve. You have to work on some 700+ questions, otherwise your score will predictably converge to your old/previous level...
Be very honest about (keeping track of) your mistakes - record them religiously, together with the time it took to solve each question - if it took too long - consider it an error. No one will be seeing and judging you for making a large number of errors in your preparation - only you will, so record them, being brutally honest, and revise them - this is your best tool - your customized
error log... it's like testing holes in your firewall or cracks in a dam...
Good luck!