The Kaplan method is to use about the first 5-8 minutes of your time for each passage reading it (but not as though you were studying it), and then jot down any key terms you think look important in each paragraph.
I took the Kaplan class, and this kind of worked for me, but I found that I was making the maps far too detailed. It always ended up hurting me, because It would then take me even more time reading through my map!
Eventually I stated reading the first 3 questions, and then read the passage through, and only jotting down MAJOR key words, (these are often anything the passage actually defines). As I would read the passage, I would answer one of those questions when I came to it, and then look at the next question and keep moving on in that fashion. This worked much better for me, and I started getting 22-23 regularly. After talking with my Kaplan teacher, she said that this is how she actually did it.
Then the night before the DAT I was taking a full practice test and I found that I was just about out of scratch paper, and I wanted to use the rest on QR, so I didn't really make a map. Instead, I read through every question (not the answers) for each of the 17 or so questions for a passage in detail, really noticing key words, and then I would start to read the passage. Any time I came upon any word in the passage that looked like it even might be a key word, I went through the questions looking for it. I was able to answer about 80% of the questions the first read through, and then I just hunted around for the remaining ones, and if I was looking for one answer, and found words sounding like they may have been related to another question, only then did I jot a quick note down. I didn't think I was going to do very well, but I ended up getting a 29 on the practice test.
So, pretty impressed, I tried that on test day and I ended up getting a 30 in RC. 😀 So try it out! I know everyone has their own strategy for RC, and this might work for you! But be careful, it may be risky if you're a slow reader, but I usually finished each section with a minute or so to go. Good luck!