After taking my grandmother around to hundreds of garage sales when I was a teen, I began having sales when I was married. Here are some of my tips:
Setting Up
Great signage is one of the single most important factors that can make a sale a success! Not just a good sign, but lots of good and accurate signs with arrows at all possible points. Write them on bright colored poster board or glue this onto weighted boxes at the most strategic points; corners, intersections, and medians (if not illegal where you live). Without breaking the law, there are ways to get around it if you cannot "attach" to a telephone or public utility pole, or if a land owner thinks they own past a sidewalk to the street. Get permission from an owner before placing a box at their corner, home or retail location.
Have the garage sale on the weekend, Friday to Saturday, then possibly Sun, 1:00 PM to dark, is a good way to avoid problems.

Make the sign with a wide tip permanent marker in dark large lettering.

Cover the lettering/sign with clear plastic and tape in case of rain.

Well in advance of the sale, drive the area and study where the traffic flow/reasonable eye-sight and distance from stopped traffic and from the ongoing traffic view is. Giving the potential buyer about three car lengths to see and assimilate the sign info is critical. The good thing about using a mid sized box with a large rock to weight it down is that it is not likely to blow over, nor is a disgruntled buyer as likely to knock down your sign or steal it outright, as was my experience one year.

The morning of the sale, put your cash box and signs in your car and drive to put them out, before your sale begins. I find that hours complicate things, so I recommend describing exactly where it will be in the title: use, yard sale, garage sale, driveway sale, patio sale, lawn sale, sidewalk sale, or neighborhood, church, or private sale, helps the buyer to prepare and to look for the location without such stress. You may know where you live, but they do not. You are trying to draw them in, not keep them away, right? Use correct arrows to help them. Do not use a sign with the arrow in the wrong direction. Take a hammer if using a sign, and plenty of medium rocks, if using boxes. Plan no more than you can carry in one or two trips.
Dress well when you place them out, because some buyers will see you right away as you are placing the boxes. Have some adult at your home while you are gone, because you cannot beat the first buyers from the first box/directions, back to your home. Have your cars placed in front of your home, out of the way in your driveway, and if necessary, use the car to place a "Sale Here" box on top of the car, for those to see from a distance who are near and driving up wondering where your sale is.
I will not shop a sale that has no prices on the items. I use a roll of narrow masking tape and write the price/short description on every single item the week/day/night before.

I will not shop a messy, dirty sale, with things thrown all over the grass with no care. Take the time to use whatever you have to display items in some reasonable order to make your sale, "buyer friendly". I tend to think a seller is sizing me up in order to judge what I might be able to pay, and am offended and not likely to buy anything at all. Remember that your sale is not the only one in the city. Your things may not be as important to others as they are/were to you. You're not a retail store, nor are your things always another man's treasures. In fact, most things are truly junk, not treasures, I believe.

In the heat of the summer, place the sale under the shade of a tree or set up patio umbrellas, or an inexpensive canopy. If cold, have it inside a warm garage, or defer to spring/summer/fall.

Pricing And Selling
The rule of thumb is to price about 10% of the original value of the item, unless new, then you can double it, or take "offers" and the chance on whether they want it or not.
When using masking tape or labels for prices, attach them to the inside of lapels, underside of collars, and not on any outside area, because the sun can melt some of the adhesive to fabrics or plastic. Another way to price is to have a large well placed/written poster near the cashier area with summaries: dresses $____, blouses/shirts $_____, shoes/bags/hats $ _____, furniture as marked.

Remembering that in most cities, there are limits to the number of days one can have a sale in their home. Ours is three days, three times a year, i believe. I forget from year to year, and suggest that you check. Regardless, keep in mind that you only have a few days to make the sale and move your things out of your way for some price. Put enough thought into it that you decide in advance, not at the sale, what is your minimum price, because most want to "bargain" for the lowest price, usually asking, "Will you take $________for this and this?"

Choose found/used doors covered in table cloths for sale tables on top of lawn chairs, smaller tables, TV trays, tire stacks, boxes, etc.

Try not to sell too much at a time. It's confusing and messy.

If it is your first sale, be very careful because you may not know the value of your belongings passed down to you from relatives. I lost precious items this way, only regretting it later. Get books from the library about what is more valuable at a sale. Remember that collectors buy one at a time, usually, and go to other sales to get familiar with pricing in your area.

Do not keep a cash box in full sight, but rather use a fanny pack around your tummy and keep it zipped up and in front of you, keeping a sharp eye and feel on it at all times. I have had two cash boxes stolen off a table next to me at sales.

Keep a calculator handy inside your fanny pack rather than to rely upon your scrambled memory at the moment. Keep whatever large bill an individual has given you in between three fingers of one hand, while you give/count change with the other, so there is no misunderstanding about the correct change. Remember that you cannot deplete your only change (starting with about $25 at the beginning of the sale, in mixed bills/change of quarters only).

Also, in this day and time, with so much crime/poverty rampant, watch children who walk out with things in their hands, watch adults who wear jackets/hats, and groups where one tries to keep you engaged in questions while the others steal. This happened to me several times. Do not have two cashiers. Thieves will get a price for something or two from you, pick up a third or fourth and walk to the other cashier saying that you said, $____. The second cashier will shout the price out to you and you will not realize it was not just for the items you quoted, and cannot see the extra items in the buyer's hand(s). Save and use every possible bag you have so that everything gets bagged as they leave the sale. This way, if someone carries something out in their hand, you can more easily see it.

Always have at least one other adult as a helper/substitute for when you need to take a short break for any reason. Two more helpers is even better, so that one can always watch for thieves.

I like a sale that divides men/women/children/ family/infant areas, to make my shopping easier, friendlier. Also, do not set your prices too high, and do not reduce your asking price too much, to avoid those who want something for nothing. Save that for the very last hour of your sale, and you will have to bargain, often time for the whole remaining lot, at a price.

When selling clothes, wash, fold, stack/hang them, to get the best prices. Good toys need to be near the check out table and off the ground. Tough, more used child-proof toys can go on the ground for testing by a child.

If selling hats/shoes, become totally familiar with them and have helpers to watch buyers head, feet, hands, arms, purses and signaling to one another. There are many scams and opportunists today that frequent all sorts of sales to rip folks off. There are also some very kind, honest buyers, but a few only appear to be when, in fact, are "dealers in disguise" who are buying your item as cheap as they can talk you down for, only to sell it for a huge profit. These often buy a lot of merchandise and use the excuse "since I am buying so much, will you take $____ for them all?" Seldom is it a bargain for you, unless it's the end of the sale and you really want to move the merchandise and not have to store it. I have "given away" items rather than have to store them, so the bottom line is yours. Once you make a decision, don't look back with regret, let it go and relax, you've got a garage sale to clean up.

Another kind of garage sale that I benefitted from was one with all "giveaway prices". This was a Christian family who would have just donated good items to charity, but decided to ask a little something and enjoy seeing who got what. It was a god-send for me when I needed clothing for cheap, because I had almost no money. I got whole outfits for $.50/1.00. The elderly need and appreciate low low prices, as well.

If you have sales regularly, as some in our area do, all rules are different, prices are usually fixed, and there's less negotiations. But when you see lots of dust and rusty junk, you can know that it's not a true garage sale, but is likely just someone who perhaps has sales for a living.

Be Honest
Don't sell anything that's booby-trapped, damaged, broken beyond repair, rotten, or contaminated without telling the buyer about it. Do unto them as you would have them to do unto you: the Golden Rule.
Be honest with yourself, asking, "are my things out of style, coming back into style, or all worn out?" Price accordingly. Listen to what a buyer is saying, especially if more than one says something. If no one is buying, either your prices are too high, your products too bad, your signs are gone/moved, or you may have something negative in the sale area, such as wrong music, eating during the sale in front of the buyers, your animals/children under foot, some unpleasant odor in the air, or something broken and obviously not worth the price.

I prefer electronic items to be together, tools to be together, and toys to be together. Have as little as possible out that is not for sale. Sold" signs on items is OK, but not too many.

I like having a table from which to buy a good cold canned drink for $1.00, And perhaps a packaged healthy snack.

Watch the ground on which you have your sale. Keep it clean, clear, and safe, so that buyers are welcomed, not soiled or sorry.

Smile And Welcome Everyone
You have taken the time to sell on little sleep and short patience with the disarray of your belongings or someone elses. Be patient. Take a multivitamin for your nerves, or have a cup of coffee before the buyers arrive. Don't chit-chat on the phone while you have buyers. Be interested in them, but give them plenty of time/space to think and shop. They'll be able to buy more, if they want what you have.
Walk around, sit little. Keep your eyes open. Act kind but firm. Wear a bright colored shirt/blouse so that helpers can tell inquirers who to pay.

I play gentle Christian music at my sales, because I believe it draws honest folks, disarms/discourages thieves, and blesses all who hear.

I watch the weather and plan accordingly, with plastic ready and available, plans for moving items in case of downpour/high wind/night time. I never leave my items outside for the next day, unless there is too much junk i'd just as soon someone steal. With every purchase, I appreciate getting a "thank you, i hope you enjoy that!", it helps in case the person might tell someone else about your sale. Also, should you have address labels to spare, keep them handy for anyone who might need to return or send another there. Don't give them out for no good reason. Have a sign that says, "all sales final" or "we cannot guarantee used items. Choose wisely and please handle carefully. If you buy or break it, you own it."

One of my most favorite signs is just outside of the buying area/fence. On a child's art easel, "Thanks for coming. God bless you." seen as the buyer leaves, and "Welcome. Come on in!" on the side seen as they come in.

Helpful Hints
Never talk to others or your helpers about how much you have made in your sale. Never lie about something. If you don't know, just say that. If you do, tell the truth, the buyer might want it anyway. Take the condition of an item into consideration as you price/bargain, and remember how much time you have left in the sale, unless you like storing leftover items for the next sale. During one of your breaks, empty your cash/fanny pack into a private place in your locked home. If you are robbed or held up, the loss will not be as great. Keep only the bare minimum and accept no very large bills for small purchases, suggesting that there is a store nearby where they can get change for it. Do not deplete your change, unless the sale of the century for a big profit. Do not try to babysit during the sale. Pick up your boxes every single PM To assure yourself of having them for morning. Good luck and God bless you!
I believe the most important things to remember are: good signage, greatest locations, price all items fairly, keep it clean, stay alert, and have pleasing music playing.

By Lynda from TX