Hi chris,
first of all, read this inspiring story. If she can do it, you can too.
from-360-to-700-q49v37-128273.htmlfrom 360 to 700 is more difficult than from 520 to 700.
Next, don't aim for 600, rather aim for 700 and prepare hard for 700( that should be the target in ur mind). If if you slip , you won't fall beyond 650 (which is still a good score for the schools ur looking forward to).
Take it as a challenge and prove urself.
As far as studies is concerned, i would suggest you to go through
mgmat set of 8 books to brush up ur concepts, and for practice use only the official material ( og 10, og 11, og 12 , og verbal, og quant) keep an eye on og 13( soon to be launched, probably april first week)..Take 6 x
mgmat tests and minimum 4 gmatprep(by reinstalling) under timed conditions..
Trust you will get more than the desired score.