Hi guys,
I'm sharing my experience because this website helped me during my preparation for the GMAT. I hope my tips can help you.
I had not given any test in a couple of years when I started. However, my score on the diagnostic test (taken without any prep) was 700. This was because the GMAT is not based on any technical knowledge but rather logic. This is one of the most important things to know. Unfortunately, it means either you have it or you need to work really hard to develop it. I believe that if you get anything above 650 in the diagnostic test, you are ready to give the GMAT in 2 weeks time. Additional prep will yield diminishing marginal returns.
So how did I get +50 in 10 days? This part is more important. Initially, I thought I did not have the technical knowledge in Quant so I went over the Quant concept chapters in 2 books. This took about 4 days and was a complete waste of time. How did I know? I took Test 2 (GMATPrep) and only got a +10 increase in my score. Most formulas & concepts are fairly basic, but a quick refresher may help if you're completely out of touch with them. Just don't spend too much time on it.
So what should you spend time on? Two things only: (1) Timing (2) Stamina.
(1) Timing --> This will make or break your score. I figured this out after Test 2 and then did as many additional practice tests as I could, ALL of them timed. Doing practice questions without timing is almost useless. Most people can eventually solve the questions, but the real job is solving them in 120 seconds. This will force you to (i) work under pressure (ii) look for shortcuts in solutions (iii) understand your limits. Part (iii) is important because it will give you an idea of how many questions you will need to leave. Do NOT try to solve all questions. I was initially stubborn and tried to solve all questions but this would mess up my timing. Eventually, I accepted I will have to guess 3 questions. This changed everything; now I would skip the most difficult questions and have more time for the easier ones. I found out I could still get a decent score despite guessing a couple of questions. It is however, also important to know which questions to leave and which to attempt. This you will figure out as you practice. A GMAT instructor friend told me it is possible to leave up to 40% of the questions and still get 700+ (I cannot verify this claim however).
(2) Stamina --> This is fairly obvious but I suspect few people train for it. Your GMAT performance will depend GREATLY on how alert you are. Hence it is important to train your body and mind to be 100% alert for 4 hours. This is achieved only through full practice tests (with all sections, including essay writing). I must have done about 8 full practice sessions before my body got used to it. Train your body otherwise you will perform poorly, especially in the last 2 sections (which matter most). It also helps immensely to do practice tests at the time of your appointment (morning or noon) for at least a few days before the actual test.
Once I incorporated the above two elements, my score shot up. Three days of this meant I was averaging 770 in the official practice tests. Practicing the above two also gave me confidence since I knew I was well prepared for the actual test. Despite a minor hiccup (I could not get any sleep the night before), the actual test scenario was pretty smooth for me. I ended up getting a 750 (blame the lack of sleep).
Additional Information:(1) If you do score under 650 on diagnostics, then I recommend going through the Quant concepts in detail. Also do lots of timed practice questions, because this is the only way you will build your logical thinking skills. This might take several weeks though.
(2) Buy the official GMAC Test 3 & 4 and the Question Bank. This is the best source to practice. They had a coupon sale so you might get it slightly cheaper. If you cannot afford it, PM me and I will share my details with the first person who does so. If you have time, go through the questions in
the Official Guide.
(3) I found the actual test to be about 10-20% more difficult than the official practice tests (Quant only). The other sections were more or less similar.
(4) Build a essay framework before the actual test and just use that. This means that the first few and last few sentences are general and should be memorized and replicated, regardless of the topic (this is applicable to more than 95% of the topics). This way you'll not struggle to begin your essay (usually the most difficult bit). Also, I feel that the opening is important for it gives a good first impression to the human examiner. Also, a longer essay helps a lot. Just keep typing if you have time. I got a 6/6 on essay with literally only 2 hours of prep, and I am a non-native English speaker.
(5) I don't have many tips for the Verbal section unfortunately. This was something that just came to me easily. However, the 'Manhattan Sentence Correction Guide' was probably the MOST important single guide for me. Do not go for the GMAT without reading this. I found that it helped to summarize the entire book in 1 page and to memorize those strategies.
(6) I found this guy's experience to be useful: [Can't post link, sorry]. Search 'Hacking GMAT in 8 days by Laksh' on Google. Followed quite a bit of his advice.
Hope my experience helps. Good luck!