I am stuck at 680 for the second time (in 1 week) in manhattan practice test.
When you take two tests in a week (or 1 week apart), the typical expectation is that you'll get about the same score. Progress generally isn't linear - most people don't get better on some sort of steady basis. Rather, we make jumps (as you found in your 630 to 680 jump).
The bad news: what you score on a practice test taken under 100% official conditions (including the essays) about 7 to 14 days before the real test is approximately what you should expect to score on the real test.
There is some sort of good news, too, but I have to explain something before I tell you what it is. These tests all have "standard deviations" - meaning you are expected to score within a range, not that exact score, if you keep taking the test. The standard deviation (SD) on the official test is about 30 points; the SD on our test is about 50 points.
This means that, if you were to take the official test and score a 680, and you could then somehow take it again the next day, you would have a 2/3 chance of scoring in a range of + or - 30 points from your first score. Ditto for our test, expect it's +/- 50 points.
So, the somewhat good news is that you are technically already within range of that 700 score you want.
Now, I have some questions for you. Did you take these tests under 100% official conditions, including the essays, the number and duration of the breaks, and so on? (I see that you did take the essays on the last one - that's good.) If so, then your score is more likely to be a valid representation of your current scoring level. If not, tell us how you deviated from official conditions. If you deviated a lot, then that would make it more likely that your practice test score was inflated.
So, now you have to make a choice. If you absolutely must have a 700 minimum, then you should think seriously about postponing your test until you take at least two tests under 100% official conditions that hit 700 or higher.
If you want the 700 but would also be okay with a high-600s score, then you can are likely in that range and can feel confident keeping your test date ASSUMING you did take your practice tests under official or close-to-official conditions. (If you skipped the essays and used the pause button periodically, for example, then your score is likely inflated.)
If you haven't taken the test before, you might consider taking it just to see, and then just taking it again if you don't hit the 700. (Schools take your highest score.) Be aware that you have to wait 31 days before you can take it again, so go check any deadlines and see whether you'd have the time to do that.
Next, what to do for the last week before the test. This is not when you should work on weaknesses, actually. The closer you get to the test date, the more you just accept that your weaknesses are what they are, do a comprehensive review, and get ready for test day. You actually start making that switch around 14 days before test day; these two articles explain how:
http://www.beatthegmat.com/mba/2010/08/ ... -game-planhttp://www.beatthegmat.com/mba/2010/08/ ... -to-reviewLet us know what you decide to do. If you keep your test date, start doing what I describe in the two "14 days" articles above. If you decide to postpone, then do the analysis described in the below article on your last practice test and come back here to let us know the results:
http://www.manhattangmat.com/articles/e ... -part1.cfm(Note: this is a two-part article; do both parts!)