the great garage sale dilemma

We're having a giant garage sale at my church this weekend and I have rented two tables to sell my wares.  Here's the problem, if you don't know what something is, or what it's used for how do you set a price?  How do you know if someone will even want it?  On the other hand, how do I know if something I'm selling for peanuts is really worth a fortune?  Is this an antique, a collectible or a disposable?  I guess that's all part of the game and only time will tell.  At the very least, it's out of my basement!