Memorization is a very important skill to have in any learning environment. We require it ourselves in the study of chemistry. Probably 40-50% of what you learn in chemistry class is from memorization. So if that is your only method of study, you will fail the class.
You must learn concepts and be able to apply them to various situations. You must be able to apply critical thinking to all concepts and have the mental "tools" to allow you to formulate a plan on just how to solve a given problem. Read, practice, and learn to think like a chemist and become an expert so that you can logically think through any given problem.
Always keep this in mind while working problems. You will likley not see the exact same problem again. You might not even see one of "that type". You should ask yourself: "What is this problem really getting at?", "What are the key ideas that I needed to answer this problem?", "How could I take these ideas and apply them to different sitaution?". The more you dig into the material the more you will understand the concepts rather than just being able to repeat them back.