When I was in high school I spent quite a bit of time reading. (We were the only family I knew without a television set, and we lived in a place where it snowed a lot.) This led my mother to assume I liked to read. She was probably right. And that led her to tell people I was "very good at" reading. That was jumping a bit, and she was in fact wrong, but I believed her. She was my mother.
When I got to college I found that, on average, I spent about twice as long reading any assignment as other students did, but (rather oddly, I thought) had only about a quarter the retention when we discussed readings in class the next day. (My roommate could polish off reading in about a third the time and remember all of it. But then he also was handsome, spoke French, and could make up physics formulas and have them be right. I yearned to see him hit by a meteorite.)
It took me many years, a good deal of introspection, and a speed-reading course to figure out the problem: I was bad at reading. And I was bad at reading mostly because I read too slowly. Rather than tell you the details of my badness, let me turn them into a few words of advice:
I was bad at reading mostly because I read too slowly.
If a reading has an introduction (beyond just thanking people who helped), whether or not it is assigned, it is probably even more important to read the introduction than the reading itself. (If the introduction was written by your professor —as is often the case with on-line readings or course readers— the chances are that the introduction hints at what exam questions about the reading will probably ask.)
Spend not more than one minute looking through all the pages of an assignment before you read it. That will let you see what it is going to be about. (This sounds stupid. Don't worry about that. Just do it. It helps. A lot.)
Spend not more than one minute looking through all the pages of an assignment just after you have finished reading it to review what it was about. (This also sounds stupid. It also helps. Even more.)
Do not let your mind wander as you read. Pausing to reflect on the implications of what the author is saying is a good thing; planning your weekend while your eyes continue to pass over the text is not.
Run your finger down the page of text as you read it. This keeps you awake, but it also tends to pace your reading speed and to inhibit your natural tendency to look back at words you have already read.
There is no perfect speed at which to read. Some materials can be read far more quickly than others —a novel is not an engineering textbook— and most materials even vary from page to page.
Avoid reading in noisy or distracting places (or with your roommate's bad music blasting in the background). The more you concentrate on the reading, the faster you will finish it and the more thoroughly you will absorb it. There are people who claim they can study better with music (or "music") playing, but I have never seen any compelling evidence that this is really so for any human, especially if they pay any attention to the sound.
(It also seems faintly insulting to a musician to read a book instead of concentrating on the music. Beethoven composed and Pavarotti sang to shake the soul and lift the spirit, not to provide the world with elevator music.)
Pay attention to the structure of what you are reading. Most non-fiction authors assigned in college pose problems and present arguments defended by evidence or illustrated by examples; they pause to tell you what they will be treating or to summarize what they have said; they provide definitions or characterizations of things, ideas, or phenomena. Noticing what is an example and what is a principle is sometimes harder than it sounds, but it makes a tremendous difference to seeing what the author is getting at. (See the essay on marking books.)
If something seems both important and confusing, make a note to raise it in discussion section. (There won't be a lot of such items. Authors are generally pretty clear about things they think are important.)
Don't look up an unknown word in the dictionary unless it seems to be (A) a cool word that you want to use or (B) an important word that you actually need. I look up most new words in English works because, as a professor, I think English words are inherently wonderful. (They pay me to think that.) When I read in other languages, I look up a word only the third time it appears, and then only if it is particularly annoying me.
Try to arrange your schedule so that your reading time comes when you are least likely to be sleepy. Reading when you are sleepy has exactly the effect you think it does.
When you finish a reading (and have spent not more than a minute looking back over it), try telling your roommate (or the wall) what it said.
Some recent research suggests that studying always in the same location is not as effective as studying in more than one place. The implication is that two quick reads, in two different places, may be a much better strategy for a lot of material than a single more intensive involvement in a single location. You could give that a try. Even if the location business turns out not to matter, twice is a higher number than once, and that ought to be good.
What counts is not what you pass your eyes over, but what you understand and remember.
Finally, do not be ashamed to skim. There is no reason why reading has to require a set amount of time, and what counts is not what you pass your eyes over, but what you understand and remember. A century ago British Prime Minister Arthur Balfour went so far as to declare, "He has only half learned the art of reading who has not added to it the more refined art of skipping and skimming." Learn to skip and skim, and you too can be Prime Minister of Great Britain.