Having a garage sale is a lot of work, but it's also potentially lucrative. If you want to save some time and stress in the whole process, only price and put out what's most likely to sell.
For my first garage sale last summer, I meticulously sorted eight years' worth of baby clothes; cleaned and researched going prices for antique, collectible plates; and dragged out boxes of books. What a grand waste of time and effort.
If I were to do it again, I'd donate the books instead and put the plates and entire lot of clothes up on eBay. It would have made prepping for the sale much easier, and I would have probably earned more on these items compared to the $1 I got from selling two books and $4 from one person buying three kid's dresses. I was sure all of the handbags I put out (for a steal) would get scooped up, but nope, no dice. I couldn't even give away some items, like stuffed animals, for free!
What did sell fast: household items (like a dutch oven, a set of lamps, and even a whole dining set, which surprised me), baby items (strollers, bouncy chairs, and tricycles, but not clothes) and new-in-the-box electronics.
Your mileage might vary, of course — I live in an area with lots of new parents — but, in general, the stuff that's easy for other people to resell at a good profit will likely get picked up faster (one professional yard sale shopper came and took almost all the household stuff to resell them at a flea market).
The Fun Times Guide has some advice on the hottest yard sale items, for further reference.