So here was my experience! Keep in mind my turnout was affected by three things:
1) it was labor day weekend and a lot of people were away
2) it was also PAX and SF comic con (I'm in the bay area, so all west coast events affect where nerds are)
3) one of the three train lines was shut down.
sooo yeah. Anyway I probably saw about 50-60 people total, and made about $500. I sold maybe 20% of my stuff, maybe less. I sold like 5 games only! that was weird. mostly cassettes tapes, laserdiscs, game magazines, and books.
Honestly I think with specialty stuff like I've got here, what I need to do is advertise those specific things and sell them in lots - it was pretty fun though, overall, talking to folks who knew about games and music who wandered in! A guy who was friends with osamu tezuka's old translator came by - unfortunately he left before I had much of a chance to talk to him. apparently that translator lives in the area somewhere.
But yeah, to the morning thing - I think that's just when yard sale people like to go! Basically 95% of the people who came to my yard sale did so before noon. After that it was just friends coming by for the remaining 5 hours.
So my currently plan is to do one more of these next saturday for two hours only, then sell the rest to local stores. I think it's worth doing a yard sale if you live in a populated enough area and advertise it on craigslist well enough!