Reading about the same concept from a range of sources can expand your understanding by allowing you to view it from a couple of author's perspectives. Mnemonic devices can be useful when you need to remember a list of facts, or steps in a procedure. Refer to the list when needed. For some courses, repetition and drill is necessary. For instance, if you have to remember how to identify all the muscles in the body, you need to practice doing it.
Memorization is necessary.