Hi,
I would say you start by taking a GMATprep practice test and figure out where you stand. Who knows you already are at your required level.
After this you can figure out what section you need to work on and then take it from their. You can go the self study way and for that the MGMAT guides are the best starting point for getting your basics clear. You will also need the OG along with the MGMAT guides.
Their are also some very good online courses (knewton, MasterGMAT etc) which you can look at if you don't want to go the self study route. Knewton actually has a 50 point gurantee.
Basically you will have to figure out what style suits you. But the starting point is a GMATprep tests to see where you stand and where is it that you need to put your effort.
If you want to go the self study way then:
I would say that the MGMAT 8 guides will be a very good purchase. How ever that said some people consider the PowerScore CR Bible a better CR guide (I however believe that both the books are pretty similar).
I would suggest that you start with the MGMAT guides. These guides make you work with the Official Guide in tandem. After each chapter/topic their is a list of OG questions to solve.
How you use the books depends. Some people would take one month for just quant. Then one month for verbal and then do combined preparation from then on. I on the other hand would suggest you switch from verbal to quant and prepare simultaneously. This way you won't get out of touch. What you can do is give 2 weeks to quant and then 2 weeks to verbal. In the 2 weeks that you have for verbal revisit the questions of quant that you got incorrect in the OG and vice versa. This will help you keep in touch with topics, strengthen your weaknesses and also at times one dimensional studying gets a little boring.
After this phase of the study (MGMAT and OG) I would suggest give another practice test to gauge your progress. And accordingly you can move on to kaplan 800 or other advanced material. In the second phase give more practice tests lot more frequently (helps you build stamina).
I think this is how you should start with your prep and later according to your new/second practice test result you can again ask on the forum how to go about your prep.
I hope it helps!!
Cheers
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