I would absolutely not price everything a dollar.
I have had a garage sale every year since my first was born...she's now 8. Both sets of grandparents spend WAY too much on clothes, toys, etc for our two kids...8 and 3. So we have a ton of stuff to get rid of...every year...especially nice clothes that look brand new.
If your clothes are nice, not too worn, stain free, etc...here's how I price. 50 cents for t-shirts/thin long sleeve shirts. Sweats 75 cents. Regular pants, nicer shirts, etc, a dollar. Whole outfits, nice dresses, good sweaters, etc...anywhere between 1.50 to 4.00, depending on how expensive it was, the quality, and what I think someone else would pay to have it. Coats...coats are expensive!! Especially considering how quickly they outgrow things...someone will gladly pay 5 bucks for a winter parka for a young child. Shoes...eh. That's hit or miss.
Toys...depends. If it's a junkie little baby toy, I go anywhere from free to a dollar, depending on it's size and usage. Larger toys, though...I have gotten anywhere from 2-20 dollars, just depending on what the toy actually was.
If you price everything at a dollar, you can perhaps expect that all of it will sell. But you can always mark things down as the day goes on, if they aren't selling...start a bit higher, if that's what you want to do.
I make a few hundred bucks each summer by doing the sale, and we rely on that money to do a lot of summer things.