Practice reading for pleasure as well as study. Reading should be second nature. Practice reading groups of words. It is a good idea to try reading newspaper articles in this way. Do not concentrate on individual words, but on phrases and groups of words. Reread the piece and check whether you grasped the meaning the first time around.
Learn the skill of reading abstracts, introductions and conclusions. This does not substitute for reading a whole article, but it will suffice sometimes if you have an enormous amount of material to get through. Practice reading sentences by just focusing on the first and last words, and trying to work out if you can comprehend the sentence.
Practice skim-reading. Take an article and skim-read it once. Write down the gist of what you have read. Skim-read again, and check if your comprehension has improved from the first skim-read. Now read the article more slowly. You may find it helpful to write down key words as you read the final time. These key words can jog your memory and improve comprehension.
Develop the skill of concentration. You can read something really slowly, and your mind wanders. This affects comprehension more than reading quickly. If you find your concentration lapsing, bring your mind back to what you are doing. It is better to take a break rather than tell yourself you are comprehending something when you are not.