Read the statement of the theorem carefully. Try to understand each and every word of it so that you won't do mistake in applying it to various situations. Then read the proof given. Understand it and try to prove it by yourself without looking at the book. Only after that, solve questions based on that theorem so that you can know what you are doing and why you are doing it.
I won't say that is the easiest way, but it is a better way to learn things. If you are not interested in learning, then just read what the statement says and you can use to solve questions. but you might go wrong in how to apply them and where to apply. You need to be careful about that.