any tips on how to improve Reading Comp skills?

Nick,

easy answer first: you will have 4 RC passages: one will be long, around 70+ and can be as long as 100 lines, usually, this one comes first or second. The second and third passages are medium length - 40-60 lines. The fourth passage is always a short one (at least people say so) which is around 30 lines. There are about 10-13 RC questions and they are spread out 3-4 with each passage.

As to improving your skills, that's a little harder. I don't know if it will help, but I can tell you what I did. (I am an international student and I got a 42 on the verbal). I have read books - as boring as I could tolerate but not as boring as to lose desire to read. I have built a little collection of fiction books I have read in the Books Review Section, if you are interested. It is not nearly what I want it to be, but it has a few good books.

I would try to stay concentrated while reading a passage. I would actually stop after each paragraph and ask myself what I read. Sort of paraphrasing the story. I also asked myself what it can mean - but I was not really concentrating on this thing. As you may have noticed, most of the RC passages are fairly predictible - 2 theories, 2 solutions, analysis of an issue, event, or some historical/political movement and its consequences. So, I would try to sort of predict in advance which one it could be. It does not matter if you guess or not - guessing is not the trick. Thinking about the passage and remembering the main points is the helpful part.
A very important and hard part is to stay concentrated and I think you have mentioned it. I sometimes would reread first sentences of a paragraph. Kaplan mentiones keywords to watch (which is easier than staying concentrated) but I watched only a few, and here is the list: (numbers such as two theories, three reasons, one major cause, etc) and reverses such as however, but, yet) i did not have enought brain power to watch for others.

If you asked me what of that pile above is the most important, I would say stopping after each paragraph and asking yourself what you have just read.

As to my score improvement. I used to miss 50% of the RC questions. I don't know what my level was on the GMAT, but I got a 96th percentile in Verbal.

Good luck, I hope this helps.