Since a few months, I had been exploring on how to study smart which applies to work as well.
After reading many articles and listening to many related lectures, the technique involves asking questions and looking into the resource to find the answer to that question. After finding answer to one to question, again try finding it validating your answer to the question. This process has to continue until you feel that you have all the questions answered.
Once you feel comfortable about the material you mastered, write a brief summary or description or article on the same which others can understand easily.
The next technique is the about focus. The focus should be so intense that you should be come part of the subject you're studying or in actual investigating. You should be like the co author of the subject and understand his point b of view.
Keep practicing this technique and keep working the results of the same for future reference.