Secret to copping cheap broadway tix?

erewhon

The lady needs to see Xanadu for X-mas. I know there are cut-rate options in NYC, but I don't know where to look and I'm trying to plan this from out of town. Is it even possible to get cheap tickets ahead of time, or do you have to just show up the day of and take what's available? Is Xanadu too hot to cop right now? How cheap is cheap? Etc. etc. Lemme know what you know. Thanks!