Memorizing pieces has always been a struggle for me. I have students who have things memorized after only a few run-throughs. Just last week I had a Level 5 student say to me let me play it once with the book and I’ll have it memorized, sure enough that’s exactly what happened. What he has is a gift but I believe for most of us the pr0cess takes much longer. Throughout the years I have developed different methods such as starting points (which I would mark with little hearts throughout my score), and studying the harmony. Below is a link to an article with other helpful hints.