I found this somewhere.. I don't remember so I can't give proper credit.
"Yes, the Fridrich Method does require you to memorize a large number of algorithms. Yes, it's difficult to memorize and keep memorized the algorithms for many OLL cases that happen only rarely. There are, however, things that can make the process less painful.
Relate patterns to one other, by shape, mirroring, inverses, finger tricks, etc. Breaking an algorithm down into smaller substeps or two other patterns is also useful. For example, #12 on my list is #45 twice with a y in the middle. While learning the algorithms, always keep a print-out page handy for reference. Feel free to edit mine by putting in your own algorithms.
One good technique for memorization is to find key shapes or blocks of colors while excuting an algorithm. For example, in doing RUR'URU2R', look at the block formed by the FRD corner and the FR edge. As you excute the algorithm, this block moves up to the top layer and is rotated clockwise 90 degree at a time before being placed back by a 180 degree turn and into the starting position. It becomes much harder to find these things for a longer algorithm, but knowing something peculiar about an algorithm help you reconstruct it as you go.
Another basic method is to "chunk" each algorithm into smaller pieces that can be excuted in one move. Each chunk should be easy enough to memorize, and then all you need to do is to piece them together to reconstruct the entire algorithm. Chunks can be any finger trick like RUR', R'UR, or B'R'U.
Of course, there's always repetition. This could be simplified with the help of a training program like the last layer trainer."