I scour libraries (I have now worn out the county's entire folk selection, not that it was exactly overwhelming in size!); I always make sure I turn up at gigs early to catch the support bands- you never know what you might miss; if I find I'm unexpectedly free for an evening, I head down to a venue that I know always has decent stuff on and a decent crowd (in my case, borderline in London); me and my mates have an intensively strict car-and-music sharing routine. We have to take it in turns to drive places, and the driver always has to ensure there's at least one tape/cd that no one else has heard yet, whether it's new or something dug up from the parents' record collection!
If the driver does not do this, they have to drive every trip until they introduce us to something. We find the threat of being the designated driver more often than necessary really boosts our music-hunting!!