I have never hosted a Garage Sale but have been to plenty & am able to provide the only perspective you need to know about.
1. Advertising: Follow the local protocol. 'Pickers' are creatures of habit. Ad in the paper, word of mouth, direction signs about 1km from home & the fireworks (balloons, streamers, signage etc) at home on the day.
2.Timing: Most Garage Sales are on the weekend & usually Saturday from 7 or 8am 'onwards'.
You will make 80% of your money between 5.30am (yes 90 minutes before it suits you) & 10 am. Be ready for the guys with torches & treat them like gold. They will buy & they will haggle & you will be the only guy that doesn't tell them to 'get lost' all day. (actually if you ask them they will say their buying day is from 5.30 to 8am - then off fishing).
Never stay open after noon. Its over! Go to golf - that's where the 'Pickers' are. NEVER EVER provide food or drinks - get 'em in & out & lighter in the pocket quickly.
Consider a day or evening outside the weekend. Advertise well & you will be the only game in town. Despite disrupting their usual routine your buyers will come, along with others who weekends don't suit.
3.Weather: There may be not a cloud in the sky but 'Murphy' says IT WILL RAIN. Have a plan so the 'Pickers' & 'Pickings' don't feel a drop.
4.Goods: Just because you want to get rid of it doesn't mean it will sell. Half of your stuff wont sell or will sell individually for 50 cents. Get rid of the garbage. As a rule, if you can't be bothered putting a price tag on an item - chuck it.
5.Display: Following on from my point above don't present your buyers with a scene reminiscent of your son's bedroom. You have already gotten rid of the garbage, now start thinking supermarket. Plenty of 'people space' between items, clear product categories & don't disturb your buyers. These people are thinking & hate distraction. If its crowded, they need their wits about them to compete with the buyer next to them - it's a race.
6. Stamina: Have a roster of family & friends. Two on in half- hour shifts at a time. The checkout chick at the supermarket makes it look easy but remember she is a professional. After half an hour you will be either bored stupid or exhausted depending on your traffic flows.
7.Pricing: Set & mark Ticket Prices but have a strict minimum clearly in mind. HAVE AN ENFORCER if haggling gets a bit 'fiery' & don't be afraid to 'check with the boss' which is a great diffuser. Remember it's your house & your property. The only redeeming feature about your 'Picker' is the cash in his pocket.
Finally, if you are able to create 'the perfect storm' detailed above - let me know. I won't turn up at 5.30am but I might just leave with an empty wallet.
Go Get 'Em,