You do not have to be an actor yourself to realize the importance of memorization. Blocking, cues, dances, and most importantly, dialogue is, I feel safe in saying, a deal breaker in the world of the stage. If you cannot memorize anything, you chances of finding a place to perform are rather nil.
It is, therefore, not surprising that I advocate working on the skill as often as you can. Memorization, like a muscle, can strengthen with usage. Also like muscle toning, the maximum benefits are achieved when the type of exercise if varied, as opposed to always consisting of the same thing.
This translates into the world of memorizing by opting to work on committing more than just monologues, and scenes to memory. Memorize poetry, rhyming, and free verse. Memorize famous non-theatrical speeches. Memorize various types of Scripture. Drilling such things into your head, word for word, will not jolt your neurons into action, but it will give you a chance to perform and recite passages which, though not intended for the theatre, will in fact enhance your performance skills.
If, however, you really want to give your memorization center a super work out once in a while, memorize things that are not intrinsically beautiful or even interesting. By that I mean paragraphs from textbooks, advertisements, and even the ingredients (in order of course) on the side of a cereal box.
Why on earth would I advocate learning such a diverse, (and in some cases dry) assortment of things by rote? As I have already said, variety is the key to any good work out. By memorizing verbatim words and collections of sentences that were not, by their nature, intended to be theatrical, we flex the memory muscles to their capacity. Without that very slight crutch that the language of a playwright or screenwriter unconsciously blends into their work, we have to work a little harder, and a little long, to emblazoned what we are looking at into our minds. Ergo, our brains are all the more ready to memorize that which actually is poetic, or theatrical, or paced perfectly for the stage.
A little of doing this can go along way. So once again, a parallel to working on physical muscles; exercise in moderation and do not burn yourself out. I think you will discover, however, that Shakespeare, or Miller, or just about any playwrightÂs script will flow freely through your mind and smoothly off your tongue after a few disciplined days spent memorizing the exact position of polysorbate 80 on your ingredients list.