I guess it matters how long it is and if you need to know it exactly, and how long you need to retain it. I had to memorize 50 to 100 word phrases and I chained them together with index cards. The first sentence is the cue for the second, the second for the third, etc. Carried them around in my pocket in order and started from first a few times a day until I could do the whole thing. But I only needed to know it exactly for a few weeks usually.