Way back in the early 1980's, our acting teacher at Pittsburgh Playhouse Theatre School insisted that we memorize, and say without any problem (using stage speech no less), the following variation of the Peter Piper tongue twister:
Peter Piper, the pickled pepper picker, picked a peck of pickled peppers. A peck of pickled peppers did Peter Piper, the pickled pepper picker, pick. If Peter Piper, the pickled pepper picker, picked a peck of pickled peppers, then where is the peck of pickled peppers that Peter Piper, the pickled pepper picker, picked?
At first, this appears to be extremely difficult to memorize (especially since she requested we memorize it on the spot in the class).
But then she gave us a trick which is nothing short of a compression algorithm. She pointed out three parts of the tongue twister that occur frequently without modification:
Peter Piper, the pickled pepper picker - this is the (relatively) hardest part;
picked - no doubt the easiest part;
peck of pickled peppers.
If we assign them "macros" A, B, and C, the whole tongue twister is reduced to A, B a C. If A, B a C, then where is the C that A, B? And that's not too hard to memorize. Indeed, I memorized it so well, I still can say it any time without hesitation.
She taught us this as a technique of script memorization. It helps, though I have yet to come up at a script that was as easy to memorize as that.