I think I go look at places like the knitting fool and other sites that have lace patterns, or look in books, find one I like, figure out the cast on for the repeats, and just knit until I either got to the length I want, run out of yarn, or just get sick of it.
Cheating is an option. . . . Cheaters never win and winners never cheat, but smart knitters who want to retain an iota of sanity do, cheerfully. ~~Kory Stamper