Set realistic time goals and number of pages to be read. Ask yourself a question before each paragraph or section, then seek its answer. This will give you a definite purpose for your reading. Take breaks when you feel unable to stay with the material due to day-dreaming, drowsiness, boredom, hunger, etc. After a short break, you can return to your reading with more energy and alertness.
Immediate recall is an essential first step toward continued retention of the material.
Recall mentally or recite orally the highlights of what you have read. Underline and make marginal notes of the key words or phrases in the section. Underlining after you read is the best way to decide what's the most important information to remember. Make separate notes or outlines of what you have read. This technique often works for more technical material which you need to put into your own words.