The first time I ever performed at an open mike was in 1962 at Gerde's Folk City in Greenwich village, and they called it a "hootenanny." No cover, just a (2 drink?) minimum. They had folks sign up for pretty much sequential slots, and mine was initially scheduled for about 10 PM, but their policy -- at least, their practice--was to insert into the roster any established acts (Paxton, Van Ronk, etc.) who dropped by during the breaks at their paid gigs. Enough of these ringers dropped by that by the time I got on stage it was about 1:30 AM and I'd had 5 hefty gin and tonics. As a result, I slurred some lyrics, twisted my tongue, missed some chords, etc. -- i.e., really sucked, at least from a technical standpoint--, but I had no stage fright, so I had a good time. The audience actually seemed to enjoy what I did,too, --no doubt because they were pretty sloshed by then, too.

Anyway, that format--letting the pros 'play through,' as it were--seemed to work pretty well. They got the priority spots but the rest of us got a chance to play, too. (And by making some of us wait till the end of the evening to perform, they sold us more drinks, too. ;-)