First simply reading will not be enough. Often times the text you are reading can be foreign and very technical material. Before you even start reading it is important to set a goal. What do you hope you learn by reading the material? What key points will you be required to know at a later date? If your answer is all of it, everything is important than you will have to work a little harder. If not, you should more properly target the information you are looking to examine.
While you are studying it is crucial that you do several things. First you will want to notice the title or header above each section. That will tell you what the section is about, and what you should absolutely understand before you move on. Also, topic sentences are valuable sources of information. Read the first and last sentence of each paragraph slowly and carefully and re-read them if you have to. As you area reading, if there are any words you don't understand it is important to look them up in the glossary or in some sort of dictionary or other reference. A few words can make the difference between comprehension and being totally lost.
After you have read the material a few times over, and familiarize yourself with it, it can be very helpful to consult supplemental material. So for a job, you might search online for something similar to what you are reading. For school websites are useful or another textbook can term words in a way that is easier to understand. Supplemental material will be a little more work, but will give you different angles on what you are studying and assist you in understanding the material.
Last, find a way to review the material. After you have read and understand the material review it a few times a day, and look over what you have read. This will help you understand it better and retain the information. Studies have shown that on average it takes several ( anywhere from three to eight) times reading and reviewing a material before it will become part of your permanent memory. These study tactics will help you read and understand information and become an asset in any realm.