After the initial greeting of a host as you approach his or her sale, there's often not much to say unless you have a specific question for them. In order to butter up the host and get a better deal on whatever they later buy, some customers will sidle up to the sales table and strike up a conversation -- but this can be awkward and forced and actually make the host very uncomfortable. There are a lot of ways you can establish rapport with the host without even saying a word, and get a good deal in the checkout process.
When you first approach the yard sale, smile and nod at the host, as well as returning whatever greeting they holler your way. And many times following that when you make eye contact, make your expression as friendly and open as possible. Even a simple disarming expression can put a host at ease and make them feel like you are willing to make a connection, something that will unconsciously make them more favorable to you in the checkout process.
As you browse the items, act interested without seeming overeager. You don't want to overplay your excitement at every little thing, or you will seem ingenuous, but if you freely express your genuine interest, the host might see it as more reason to sell you (and not someone else) the object you're planning to purchase. By the same token, don't make derisive sounds as you peruse the objects -- so no snorts, giggles, coughs, or negative words. If you spot something you think is stupid, keep your opinion to yourself, and the host will not feel looked down upon in your dealings.
One of the most irritating traits of garage sale customers is their seeming inability to put things back the way they found them. This applies in particular to clothes, which the host laboriously folded in the weeks before the sale...only to have them carelessly tossed around and the nice presentation destroyed. So as you go, fold clothes you unfold and put them back where you found them. You can even take a moment and straighten the other customers' mess, something the host is sure to take note of.
Similarly, use noticeable care when handling fragile objects. So many shoppers just wave around glass figurines, china plates, and sensitive electronics before slamming them back down on the table or display, and the host is probably sitting there gritting her teeth. Be the thoughtful person who gently cradles a fragile dish or sets a figurine down with extra care, and you will have the host on your side.
Keep your kids and/or pets under control. Nothing is as irritating to a host as a dog pulling over tables with his leash or wild children screaming at the top of their lungs as they veer around shoppers. If you make sure that your companions are well-behaved, you will often get comments from the other customers and the host ("what well-mannered children you have!"), and the relief a host feels may be enough for them to let a low price slide.
For more tips and advice on how to be a good garage saler, check out GarageSaleCow.com. It's the world's fastest-growing online garage sale community, and it's completely free!