I memorize lines with a tape recording.  I record the lines for all the actors and play it before I fall asleep at night.  I put music between the scenes I am in.  Since I have usually played bit parts and done props or dressing at the same time, I may have been more concerned with getting the lines right than doing a great job acting.  The one show in which I had a bigger part, I did not work with a tape, and frequently forgot a key line (even missed an entrance).  But I was directing too, which was a HUGE mistake.