The general answer for EVERYBODY :
PREPARATION for GMAT: STRATEGY for 30 days schedule:

[Here’s quick-n-dirty article about ‘study under a month’. Many people have aced the test by just 3 to 4 weeks of study. If you’re in time crunch, dont worry! by using right approach/ method you too can ace it.]
I presume you have sound knowledge of: all areas that GMAT tests; how GMAT works; what is its structure etc…
I assumed this because you generally register a date at least one month before. (if you’ve not, you should. …at least this is what I recommend! The early you book a date, easier it will be for you to plan a killing strategy). Lastly, of course, I assume you do get acquainted with GMAT before sending them your credit card number!
So you’ve thirty days. or let’s say, just four weeks!
Since it is much short period than ideal period to study for the test, you might need to compromise on few study materials which are not significant to you.
e.g. If you’re weak in verbal and Math is your strength you should devote more time for verbal (obviously! )
Coming to materials:
GMAT official guide 11th Edition is must:
Purchase the book immediately if you haven’t already!
As they suggested in the OG (official guide), ‘start with the diagnostic test’. Know your weak areas and know your strengths.
Repeat diagnostic test next day to see how awfully you score. Do meticulous analysis (let’s call it MA here onwards; I’ll come to it in next paragraph.) about your test/answers.
OG 11 has labeled/classified each question (which is great!). Use these tags in the future prep too….know which question belong to which category.
My definition of MA (meticulous analysis) and when & how to apply it:
While practicing GMAT problems I advise to solve at least 35-60 questions in one stretch. GMAT is more about mental stamina and patience! The real test is FOUR hours long and it tests your endurance like no other online test. 40-60 questions assures that you can sit at least for an hour at one go.
Make a table, on spreadsheet (on your computer) or on paper, of no. of rows you’ll be taking questions. And write details about how you feel about each question. This should be done while you’re doing the questions. So dont spend more than 2-3 seconds on filling the table (you can tick on pre-defined columns that will save your time). It can be used as a future reference for your study: the table should enable you to quickly realise your problem areas and which type of questions you require maximum amount of time. One session of this sitting should at least be of 35-40 questions; be it from any section: PS, SC, CR, RC or DS. (…maybe I’ll put snapshots of table if you’re still confused, please remind me at my blog )
Same amount of time you should spend in reading explanation and analyzing each answers as the amount of time you spent in answering these questions. If you got many questions wrong, increase the analysing time.
Coming back to books and materials:
You can refer basic math books, college algebra or high school grammar books to brush up your verbal and quant skills if you really wanted. But with given time constrains like “GMAT in a month” I think I would instead stick to GMAT materials. If you study smart you, over the time, would know that GMAT asks particular type of questions; and they just love to ask them that way 😉 You’ll be familiar with GMAT style if you solve more OG problems.
Refer to Official guide 11.
Check the math section of the book. Read it (~10 hours?) and re-read all its theory to know the syllabus of GMAT right. Don’t end up studying subjects that are not tested in GMAT.
Download GMAT Prep software for simulated CAT from mba.com. It’s free!
There are many other sim CATs (simulated Computer Adaptive Tests)� that you should purchase.
Check out the article to know more about these sim C A Ts
You can finish OG11 in 5-6 days (Yes you can! but you shouldn’t). Many folks I know finished it in a week (I too did it once-just for fun); but that is not the right strategy. Since the time is short you surely can compromise on other books but not on OG11.
The problems in OG 11 are arranged in ascending order of difficulty. That means, you get harder (/upper range) questions at the end of the problem sets in each section. However problem types (categories) are mixed throughout the sets. This makes many things easy in setting a study schedule. You know your level and can begin the OG accordingly 😉
They say OG11 is a bible of GMAT! Solve as many as problems you can; examine the answers carefully do the ‘MA’ as suggested above. Make Analysis chart.
Try to go through OG 11 twice in the month. (Since I’m not suggesting any other book along with OG, I think its possible to do this.) Check your progress regularly. Once you finish OG for first time you’ll get idea of how many day it’ll take to you to study one more time! If you think you have more time left you should check with other two official guides
OG Verbal guide
and the OG Quant guide.

These new two official guides, (also known as purple and green guides,) are
published when GMAC stopped the production of OG 10th edition. While new
problems are in OG 11; purple and green guides give you lot of repeats from OG
10th edition. Therefore it is wise not to buy these two books iff you already have OG 10.

Three official guides (along with the sim CATs ) are enough for a month study!
Usually, I suggest to take as many simulated CATs as possible. Practice them periodically; say, one in three-four days.
Practice tests play very significant role in your preparation. You’ll need four hours to solve each of them and two more hours to analyze them.
Since they are Computer Adaptive tests you get only one question at a time and at times, you become curious to know your score and you hurriedly complete the test. (just to know where you stand and see the answers) Needless to say: dont do that 😐 While these CATs are especially created to gauge your performance for actual GMAT, I see practice tests purely for practice. These tests hone your endurance, mental stamina to face four hour long real GMAT test! The tests are time consuming and drains your energy and hence you should keep special period for these CATs in your schedule. Be ready to spend ~6 hours for a test. Keep your cell phone on silent mode. Don’t start the test at 10.30 in the night: I know most of you out there are owls 😀 but it really not going to help in your real test. (You cant take the real-McCoy in the night, right? 😉 In fact, once you know your test times be sure to take these practice tests on the same time of the day… say: start your test everytime on 1.30 pm if your real test is scheduled on 1.30 pm of the G-Day!
——————————————————————————————–
I think this much is enough!
If I receive any comment I might add something you wanted.
To sum up the article I can say:

• Eat OG 11.
• if time permits study OG verbal and quant
• Eat OG 11 one more time
• GMAT Prep : the official computer adaptive practise test for GMAT
• Plus other CATs

Note that I have not set any particular order in this you should all of it simultaneously.
Hope that helps everyone who is in time crunch.