URsula has elaborated the process of analytical thinking in a very lucid and easy manner. I would like to add further:

Work on your habit of "Reading between the lines". There is something is front of you that writer has said, mentioned in words. There is something that he has left for you to be discovered. There is something that he has implied for you to refer.... That's where you judge, derive, make your point.... It's the same as one's body language..... A person is telling something to you with his words and telling even more with his body language...... you understand the body language, you get the whole message... Voila....

Next thing is try to put yourself in Writer's shoes. Try to imagine every next line before reading that and picture will get clear to you. By this technique, you will get additional benefit of "focusing" and it will develop your interest.....

I do hope upper mentioned words will help some one, any one......