First of all, I'm not sure that I have increased my "reading speed," I just know that I increased the speed at which I took the test. However, my reading speed may well have increased too. If that's the case, I think that it would be attributed to going to law school and practicing law for three years. This required reading large volumes of challenging, and often esoteric, materials. I'm not certain this increased my reading speed though. It did probably enhance my ability to comprehend certain types of passages. I am still a slow enough reader that I believed when I started studying for the 2002 MCAT that I would not be able to finish verbal. I was orginally going to just resign myself to reading 7 or maybe 8 passages. This was similar to the approach I used for the 1995 LSAT. I think this approach did increase my score on the reading comprehension type section. However, I think practice and adopting almost any of the strategies taught by review courses will increase your score. But to get the highest score possible, I think that you have to finish. I didn't believe this was possible until I bought the Examkrackers materials. Even when I first read their materials, I thought, "they might think anyone can finish, but they're wrong. I cannot finish." Their advise for the most part is relatively simple. Just cut out anything that will slow you down. Do not underline, circle or mark up the passage in anyway. This does not sound like it will slow you down much, but it does more than you think. You can time it and check. When underlining etc., people have a tendency to read a sentence first, then decide it's worth underlining, then go back and underline it. This breaks up your rhythm. Another thing is going straight through in order, passage 1 first, and passage 9 last. Looking for passages that are easier or harder also slows you down more than you think. The most important thing is avoid going back to the passage. Most people don't finish because they read the passage, go to the questions, then go back to the passage to find the answer, often re-reading much of the passage. Try taking a verbal section without going back to the passage at all. You may have to guess at a number of questions, but with practice you get good at guessing (there are usually only two reasonable answers anyway). If you finish with lots of time left you can go back to the passage for a couple of questions next time. I basically learned I could go back to the passage for 2-3 questions per test, and I only went back to the passage when I felt I could not make a good guess and I knew I could find the answer in the passage. Another thing that slowed me down was looking at my watch too much. Again, it doesn't seem like this would slow you down much, but it can. For me, it really broke up my rhythm. I got to the point where I never looked at my watch, and I just developed a feel for the pace I needed to keep. Lastly I had to stay extremely focused and intense! If I let up my intensity, my pace would slow (this actually happened to me in the PS section during the test and I got behind and had a little trouble finishing). I was not a person who could afford bathroom breaks. I intentionally avoided drinking any fluids that morning, and limited my beverage consumption over lunch. This was something I learned to do when I took the bar exam. I am a person who needs every second in order to finish.
But I think the thread starter wanted to know what you did to achieve that big improvement.