Cliff's Notes Version on How to Get a 770
1) Read "The Big, Overarching Principle" section below.

2) Buy the OG12 and four

Manhattan GMAT books: Sentence Correction, Number Properties, Geometry, and Word Translations.

3) Work through those four

MGMAT books carefully, taking notes on any content points that you don't already know cold (which will be a lot).

4) Search for a guide on absolute value and inequality problems and learn the techniques for attacking those questions. Or buy the Equations, Inequalities, & VICs

Manhattan GMAT book.

5) Once you've learned all the content from

Manhattan GMAT and those two minor math points, take the OG12 diagnostic exam, untimed.

6) Review any knowledge that the diagnostic exam showed that you didn't know cold.

7) Take the first official GMATPrep computer adaptive exam under timed conditions to see where you stand speed-wise.

8) Time yourself doing OG questions to improve your speed.

9) Once you've worked through the entire OG, do all 6 of the

Manhattan GMAT online CATs that come free with your book purchase.

10) Set an exam date once you are able to finish the entire

Manhattan GMAT exams in the time period and are answering questions accurately.

11) About a week before the exam, start studying outlines for the AWA.

12) Crush the GMAT.

Intro
I'm going to skip a detailed narration of how I studied, because: 1) everyone is going to work with a different timeframe and I want my advice to be as generally applicable as possible, and 2) the fundamentals behind a study plan are much more important than the specifics of the study schedule. Let's jump into it.

The Big, Overarching Principle: Content First, Then Speed
There is a finite amount of knowledge that the GMAT tests, and it is 100% learnable. Once you have mastered the content, all the GMAC can do to make the test difficult is:

a) find new ways of asking the same question

b) combine multiple concepts into a single question

c) throw in simple tricks that might lead to careless errors

d) ask a lot of questions in a short period of time (such as 37 math questions in 75 minutes)

In my mind, it is pointless to study for speed until you know every concept the GMAT is going to throw at you. Until you know ALL the concepts, big and small--for example, that when a triangle is inscribed in a circle and one side is a diameter, then the triangle is by definition a right triangle--it doesn't matter how fast you are at answering GMAT questions in general. When you face a question that relies on you knowing that specific piece of knowledge, you'll either be forced to guess or you'll have to find a circuitous route to answering the question that may not be logically sound anyway.

Know the content backwards and forwards. Take as much time as you need to learn it, and forget about speed.

Once I had finished studying content, I took the OG untimed Diagnostic Exam. I got a 100% on both verbal and math. Your goal should be the same: know everything. It's really not that much information in the grand scheme of things.

The Best Way to Learn Content is Manhattan GMAT
I did my research on these boards first and concluded that the first step in my GMAT studying process should be the series of

Manhattan GMAT guides. That turned out to be entirely correct.

I can't speak to other guides since I didn't use them, but

Manhattan GMAT will cover 100% of the content that will be on the GMAT. On the actual exam, I don't think I saw a single question that tested something I didn't know, and any questions I missed were because I made a careless error or I was running low on time and had to guess (and that was only one question). The

Manhattan GMAT guides are also very compact: they don't include any extraneous content that isn't tested on the exam.

The 4 absolutely essential Manhattan GMAT guides are:
1) Sentence Correction - As everyone here points out. Even if you are an excellent native speaker and writer, there are many, many grammar rules that the GMAT tests which you won't know. What "sounds right" to your native ear is in many cases wrong.

2) Number Properties - Because no matter how naturally good you are at math, you won't be able to figure out the properties of a consecutive set of integers in the 2 minutes you have to answer a question.

3) Geometry - Same as #2, except insert "properties of an angle inscribed in a circle" instead.

4) Word Translations - Nothing in here is too advanced, but this book fills in the topics that aren't covered in Number Properties and Geometry: rates & work, combinatorics, probability, statistics, and overlapping sets.

I also purchased Equations, Inequalities, & VICs, but the knowledge in there can be attained by searching for guides on inequalities and absolute value problems. The guide has a few other tips for how to approach different types of questions, but it's not nearly as essential as the four I mention above.

How to Use the Manhattan GMAT Guides
There are probably a few ways to approach this, but the method that worked for me was:

1) Read through each section carefully and take notes on everything I didn't already know cold (which was most things). For example, I knew that all triangles have interior angles that add up to 180 degrees and I remembered the formula for area, but I didn't remember that the sides of a 30-60-90 triangle were in the ratio of 1-2-root 3.

2) Make those notes comprehensive enough that I wouldn't have to refer back to the book later. This will save you a ton of time in the long run, because you WILL need to review these concepts repeatedly in order to know them cold.

3) Do the problems at the end of each section. It's really helpful to apply all that knowledge you just learned.

This will take you a long time. The Sentence Correction guide in particular will take forever, as it is gigantic and there will be many things you don't already know. However, going through these books will be far more effective than just whipping through questions in the OG and trying to learn concepts from their explanations of the answers.

Once you've worked through the Manhattan GMAT, take the OG untimed diagnostic
It's important to take the diagnostic untimed, because you want to see the upper limits of your knowledge of the exam's content. If you're working too q

uickly, you may make some careless errors or not have time to think through the complexities of the more difficult problems. Focus on getting the answer right, and you'll work on speed later.

The diagnostic will tell you if you need to work on any areas not covered by the 4 essential

Manhattan GMAT guides. (Personally, I was naturally very strong in verbal, so I didn't have any trouble with Reading Comprehension, and I did well enough in Critical Reasoning that it wasn't worth putting too much focus on it. You may be different.)

The diagnostic will also tell you if there are any areas in the 4

Manhattan GMAT guides you need to re-focus on. If you missed any questions because you didn't 100% know the concepts behind it, go back and review.

Once you know the content, take a GMATPrep exam to test for speed
Once your untimed diagnostic proves you know the content (or proved that you didn't and you went back to review), take one of the official GMATPrep computer adaptive exams. This will show you how you perform under timed conditions and will reveal where to put your focus on next.

It turned out that I was 100% fine on verbal and could finish the section with >10 minutes to spare. However, I really had trouble finishing math when I took my first GMATPrep, and I didn't even get to the last 7 questions in the 75 minutes. Thus, I knew I had to focus most of my speed training on math.

Once you know the content cold and you know where to focus, practice for speed
I'm sure there are 1,000 different ways of doing this, but the one that worked for me was:

a) Choose 10 questions in order from the OG

b) Time myself doing them

c) As I work through, mark any questions that I wasn't 100% sure I got right

d) Check the answers and additionally mark any questions I got wrong

e) Go back and review the questions I got wrong to see if I could figure out the right answers without looking at the OG's explanation

f) Review the explanations for questions I was unsure about but still got right

g) Take notes on any tricks or pieces of knowledge I didn't already know cold

With the math section, I started off sometimes taking over 25 minutes to do 10 questions, but by the end, I could do even difficult math questions in 15-18 minutes.

Going through the entire sections in the OG also has the pleasant side effect of revealing any gaps in content that you may still have. I found that there were many points that seemed very minor when I was first working through the

Manhattan GMAT guides but that turned out to be essential for answering a question in the OG. Use this opportunity to review, until you know even the smallest details cold. The

Manhattan GMAT guides are really, really good. They don't include extraneous information that the GMAT doesn't test, so know absolutely everything they say.

Once you're done with everything you can practice in the OG, use the online Manhattan GMAT practice CATs
A set of 6 computer adaptive tests is free with the purchase of any

Manhattan GMAT book, and the exams are pretty good (and supposedly better than any other prep company's unofficial exams). A few notes about them to be aware of:

-A lot of the

Manhattan GMAT online math questions are very computation or algebra-heavy, and that's what makes them difficult. In contrast, rarely will you have to work out crazy algebra on official GMAT questions to get an answer. Just be aware of this. If you can finish 37

Manhattan GMAT math questions in 75 minutes, then you should be able to go even faster on official questions.

-Some of the

Manhattan GMAT verbal questions are just retarded. Critical Reasoning, in particular, has some questions on which the correct answer's logic doesn't make any sense. Ignore them. Every question on the real GMAT will be sensible.

-Like with the OG speed training, mark questions you're unsure of, so you know which ones to review later.

Once you are finishing Manhattan GMAT practice exams in the time allotment and getting a decent score, make sure your test date is set
I got through about 2 full CAT exams when I figured I would be ready in a few weeks to take the test, so I signed up. Just bear in mind the lead time required to book an appointment in your area. In Los Angeles, the earliest test date I could initially find was 8 weeks in the future. However, I found a cancellation that was about 4 weeks away, so I jumped on that.

About a week before the exam, start glancing at the Analytical Writing Assessment
Everyone treats this as mostly an afterthought, and if you're a native speaker and writer, it probably is. It did help me to look at a few templates for how people should structure their essays. This one was pretty good:

http://www.platinumgmat.com/about_gmat/awa_essay_template
I ended up with a 6.0 on the AWA, and really, I think the keys were:

1) Have a large quantity of substantive points for both essays. For the Analysis of an Argument, in particular, there were a ton of different criticisms to make. Cover as many as you possibly can, even if it doesn't fit neatly into one of those prebuilt outlines. Even if one of your paragraphs is two sentences, that's okay: "The author also mistakenly assumes

. This is faulty because but could be improved if ."

2) Write A LOT. If you look at the sample essays with grades in the OG, the first thing that should jump out at you is that the Score 6 example is long, the 4 example is shorter, and the 2 example is the shortest. No matter the stylistic quality of your writing, the more substantive words you get onto the page, the better your score will be.

Take the test!

If you do all of the above, you'll rock it.

A Final Note on Attitude

My general attitude my entire life towards standardized tests has been, "Given unlimited time and patience, I'm perfectly capable of getting a perfect score. Let me work hard to prepare and see how close I can come to that perfect score on test day."

Unless you're Rain Man or some child prodigy, you're not going to walk into the GMAT and pull an 800 out of thin air. Even if you're incredibly well prepared, chances are there will be one or two questions that will throw you for a loop and you won't be 100% sure of your answer in the 2 minutes you've allotted to find it. That's okay. Prepare the best you can, and a good score will follow.

The best definition of confidence I've ever heard is, "I did it yesterday, I'm doing it today, and I will do it again tomorrow." Know the content cold and practice for speed (yesterday), take the practice tests (today), and crush the actual GMAT (tomorrow).