Great suggestions below. I agree about keeping an eagle eye on your cash. Have coins - you'd be surprised how many people want to pay 25 cents for something, so have at least $100 in cash ($10, $5, $1 and a roll of quarters), and wear an apron with pockets or a fanny pack. Put the bigger bills in an envelope inside that pocket.
Definitely have plastic bags and newspaper for wrapping things, even some old cartons (get extras at the liquor store for free). Turn boxes on their sides to create "bookshelves" so people can read the spines of books.
Clothes - you will spend a lot of time refolding what people go through and mess up. Consider a drying rack or stringing a clothesline - we used a long rip with loops tied in it every foot or so, so that things didn't slide any farther than 1 loop. Prepare to have that line sag over time so have a plan to hang it higher or tighten it up.
If you can't tag everything, put a sheet or tarp on the ground (or several) with a sign that everything on this sheet is $1 and everything on that tarp is $2. If you have electric items to sell, have an extension cord hooked up to your garage or outdoor outlet so people can make sure things work.
Assume that people will start arriving 60-90 minutes before your start time even if your ad says "no early birds". They don't care. You can still be setting up but this is when the real collectors come, to find the best deals on stuff you don't know the value of. Be prepared for people in search only of specific things - china, jewelry, record albums. Don't be upset if they leave without looking at everything else.
If your goal is to get rid of stuff almost without regard to price, be prepared to knock down prices early, price things in groups ($1 each, 7 for $5 etc.). And put out a table for free stuff - if not at the beginning, then halfway through.
Have a plan to get rid of stuff at the end of the day - donate it, go to the dump, schedule a pick-up for Monday morning by Big Brother/Big Sister or anyone else with a truck. There are "junk" services that will come and take stuff away for a fee, and then sell or dispose or donate as they see fit. There's a fee for that so investigate - but you don't want to bring stuff back in your house!
If you can't sell everything you own in one weekend, fine. Choose what you can display easily and attractively, and get it out there. You can have another sale later on - unless this is a moving sale and you don't have time.
If you haven't run an ad on Cragslist, do so. In the future, send an email to your neighbors asking if they want to sell on the same weekend - putting "multi-family yard sale" in an ad brings in way more traffic, even though you are sharing shoppers with others.