Not Crossing 640 in manhattan. (Q 44 and V 34). Need help

First, I'd encourage you to linger in these forums more often. It adds a lot of value and you gain a wealth of knowledge.

Fortunately or unfortunately CR and RC are two areas where (only) practice can take you a long way. You need to solve tons of problems and develop an ear for the GMAT problems. Once you are through with 100-200 official CR problems you will start to observe patterns in the questions. Almost always there are opp. answer choices, out of scope choices, too narrow answers etc. CR Bible is a pretty decent book, and if you are through with the concepts, I'd encourage you to practice through the GC forum (do use tags).
Try to pre-think the answers - helps immensely. If you are not familiar with the concept, please search through posts on GC (or google) and you will find a lot of good videos. (there was one session held by e-gmat recently on this)

RC is the most boring section of the test for the majority of the test takers. The only way to excel in it is to read GMAT-like material (economist) in your free time and do lots of passages. Break the questions into the following:
according to the passage - answer is in the passage
infer/suggest - answer is not explicitly stated in the passage
try to pre-think the main point of the passage.

for SC: you might also want to consider Aristotle grail.

Quant:

you haven't mentioned any material, so I assume you haven't done a very structured study yet.
Manhattan guides would do for the starters.

practice tons and tons of questions from these forums. Reach out to fellow members and learn as much as you can from bunuel's posts.
start with NS, algebra, geometry and co-ordinate. Do basic P&C and probability questions - don't jump the gun there. Also, try to do 15-20 questions at a stretch - helps you grasp the topic and builds stamina.

you may put kaplan 800 on hold for now. You would do well to master 650-750 level questions for now.

Whatever you choose to do, you should be thorough with the OGs, supplements and the question pack.

good luck

You have just listed the name of a couple of books, including ours,but you haven't mentioned how did you use these books. One important thing to remember is that using more and more number of books is not going to help unless you use them the "right way". Think of it this way: Two men work out in the gym. One man complains that he does the same exercises and the same number of reps in each exercise as the other man, yet he's unable to lose any flab while the other man uses the same machines, does the same exercises yet he is able to build muscles.
Think about why the second person is able to build muscles while the first person isn't inspite of having the same "resources"? The simple reason is that the second person was doing the exercises the right way, was taking the right amount of break in between the exercises, was taking the right nutrition and above all understood the important of giving his body sufficient rest after coming back home.

So what parallel can you draw from this analogy for the GMAT ? That you need to study the right way(Refer to the The Right and The Wrong Way to Study for the GMAT in our free ebook The GMAT Demystified). Do you analyze each question well ? Do you understand why you got a question wrong ? Do you log your mistakes, especially in SC, in an error log ? Do you try to solve a Math question through alternate ways ? Do you know how to apply a concept-or is it that you just know the theory inside out ?
There are some of the points you need to think about and once you have figured out the answers to these questions, your scores will automatically start improving.