I first took the GMAT in Dec 2009. I studied for a little less than 6 months and received a 680. I was upset because I had hit 700+ in many practice test. I self studied for this test using MGMAT book. Part of the reason I was doing well is I had just graduated college and had taken a lot of quant and english courses in my senior year. I ended up meaning to retake the test, but never could get back into the swing of things to study.
Fast forward to June 2012. I decided to start b-school applications and really felt like the 680 score was going to weigh down my application at my top choices. So I decided to try and retake the GMAT. I enrolled in MGMAT classes, and studied, I took the GMAT in Oct. I really struggled on practice test. I got a 640, such a large drop from my initial score. My verbal went down a lot, and my quant went up slightly. I was really bummed out.
I had been using BeatTheGmat.com for a while now. It is the best place to get answer explanations. I really liked Mitch H's aka GMATGURUNY https://www.beatthegmat.com/mba/experts/mitch answers. I contacted him through the forum to set up some tutoring.
Mitch was an amazing tutor. My quant score improved tremendously. I met with him 2, sometimes 3 times a week for two hours at a time. I don't think I would have improved at the pace I did, if not for him. He was also very attentive with giving me homework, checking in on me to see how I was doing, and making sure I understood things. He even emailed me right before my test to wish me good luck. I highly recommend that anybody (specially if you live by NYC), that needs to improve their score and only has 1-2 months, email Mitch. When trying to get into a top MBA school - its not the time to try and save a little dough. Not to mention, Mitch is very reasonably priced. Much less than an MGMAT tutor.
Test day was a little crazy. My test was pretty late in the day after work. I actually went to work and freaked out for a 10 minutes because I thought I was not ready. But then I calmed myself, walked down to the test center (w 44th street), and got myself excited.
I actually ran out of time on both sections. I had to finish last 3 quant within a minute each. For verbal I had 6 questions left with 6 minutes, including a reading comp! I didnt practice well with pacing. So go figure. When my score screen popped up with a 710, I actually hooray-ed in the test center. Woo!
Materials: I own every GMAT material there is (just kidding, but its a lot). Few OG"s and the extra OG books. The MGMAT books, GMAT Hacks, and several other guides. I recommend making your own study guides from all the guides and books out there. This helps you organize the best of each option. For example, I liked how GMAT Hacks did remainders vs MGMAT. So I put just their remainder stuff in my guide (my guides are available, will post later... for free).
Tutor: Don't be cheap, get a tutor if you need it. Worry about recouping the money after you get into HBS

Motivation: Find some. Mine was my family, girlfriend, and dreams.
I BEAT THE GMAT! Good luck to everyone trying! It is possible!
Best,
Benjiboo