If you've never organized your own yard sale before, don't worry: It's not brain surgery. It is, however, something you'll want to prepare for and put some thought into.
Address each of these basics, and you should be well on your way to a successful sale:
Plan ahead -- Just decided you're going to have a yard sale? Great! Now give yourself at least month to pull it together. In addition to gathering up and assessing your discards, possibly recruiting help, and preparing and placing signs around the neighborhood, you also need to find out whether your city requires a permit and whether your home owners' association or other neighborhood organization has rules about yard sales (it's likely they at least have ideas about where you can and can't put your signs).
Get help -- You probably don't want to do this all alone, since your attention will be spread pretty thin during busy sale periods. Ask a couple of friends, neighbors or family members to help you out with set-up, running the "register," or clean-up -- or better yet, to add their own wares to the sale! Multi-family or neighborhood-wide sales draw more buyers.
Advertise -- Some yard-sale shoppers have a sixth sense about these things, but most of your potential buyers will need you to actually tell them you're having a sale. You can pay for an ad in the newspaper (which is really only cost-efficient if you're having a multi-family sale, so you can all split the cost), but there are lots of ways to advertise for free. Craigslist and yard-sale-specific Web sites, neighborhood newsletters, grocery-store bulletin boards and handmade signs around your area can all help spread the word.
Make it look good -- If you're going to the trouble of attempting to sell your stuff, make it look appealing so it actually sells! Wipe down appliances, wash, iron and hang clothing, and lay everything out nice and neat on clean tables and shelves, not in piles.
Direct -- Make it as easy as possible for people to find your house on the day of the sale. In addition to putting your address in all of your ads, you might want to put up arrow signs starting at the main road on the morning your sale starts, so nobody gets turned around and gives up.
Be safe -- Remember, these are mostly strangers coming over to browse your wares. Do not let people in your house to try on clothes or use the bathroom, and keep your doors locked. Don't take personal checks from strangers, and rather than a cashbox anybody could grab, keep earnings on your person in a fanny-pack-type device or safely in your pocket. Take periodic trips inside to deposit the cash.
Price everything! -- It will definitely take you more time, but put price tags on every item rather than just waiting for someone to ask, and avoid the "all blue tags are $1" system, which mostly just annoys people. It's much easier for the shopper if each item has a clearly stated price in plain sight. You'll sell more this way.
So, now that the basics are out of the way, let's get to the good stuff: What do you want for that TV that hasn't worked since the '90s?