You want to have PLENTY of change, too. Tons of people will have hit the ATM on the way to yard sales so they'll show up with a $20 and want to buy $2-$5 worth of stuff.
Clothes that are hung up sell better than folded clothes, so hang a few of your best items (on a rack, fence, tree limb) and as those sell, replace them with other items. Tools and furniture placed where they are easily seen from the road will get the guys to stop, too. My stuff gets cheaper as the day goes on or I throw in something for free. You bought 2 shirts and 3 books? Here, have a pair of shorts or another book free! That way I get rid of most everything. Whatever doesn't sell does NOT go back in the house or garage, it goes in the car for donation drop off on Monday.
Good luck!