my experience was somewhat similar, but not as drastic (prep test avg around 650. actual gmat 580). i found a disconnect between the prep materials (i.e., mgmat, kaplan, and the GMAT Prep software) and the actual gmat. the prep materials were significantly easier than the actual gmat.

a couple of things that i'm going to change the second go around:
1. focus mainly on the OG prep.
2. disregard most of the gmat prep cat's reading comprehension essays--the actual gmat reading comp essays were much more longer and distorted (time issue) than the ones that were on the gmat prep.
3. large disconnect btn the mgmat and og quants. next time, focus all of my energy on the og quants.
4. master the most basic perms/combos/probabilities and move on. i spent way too much energy on these questions. only saw one of them on the exam.
5. mgmat sentence correction is great, but the mgmat verbal cats are misleading because the og gmat verbal section is much more tougher and convoluted.
6. i'm going to test and then reinstall the og gmat prep like 300 times.

First of all, work on a timing strategy. If you look at my debrief post, you will see an outline for a decent timing strategy to keep you on track.

Secondly, I do not think you should try to implement everything in the MGMAT SC book. Pick the top 3 most important things and focus on those e.g. subject verb agreement, parallelism, pronouns)

looks like we're on the same boat...my story's pretty similar except that i had more of drastic drop and i still can't figure out what went wrong.

my first attempt was miserable but didn't prepare much so i was able to let go of it.

2nd attempt,which was about a week ago, i was well prepared and scoring on the mid to high 600s on all the MGMAT cats and GMATPreps with couple of low 700s. i thought the least i could get on the actual gmat would be a 650 but ended up with 530!! with Q 37 and V 26 (don't have the paper in front of me but i think that's about right).

i'm planning on doing much of GMATPreps, although I've already done it like 5 times...and review OG stuff but i started to realize that i pretty much memorized most of the Qs so i'm not sure if it's worth it...

well...hopefully the 3rd time is the charm for both of us...i just wanna get this done and over with...good luck to u!

Thanks for the advice

i was depressed for whole three days after the exam and then i thought if i don't give it another shot all the things i studied for would go to waste...so i just went ahead and scheduled one for jan. 9 (about 5 weeks since the last exam) i'm starting to realize i'm kinda short on time with holidays coming up and end of year chaos at work...but i don't think pushing it back would be necessary as long as i utilize my time effectively. i'm planning on taking at least 5 more GMATPreps (i already took 1 MGMAT and 1 GMATPrep over the past week and a half...and scored 700 and 740, respectively...my practice test scores are keep increasing...more of a reason why i'm so confused how i scored so low on my real one...) and thorough review on OG books (all 3 of them) on their 2nd half of each section...hopefully that's enough prep for the retake.