Have signs with BIG ARROWS that can be seen from at least a hundred feet away. You might want to do a test run to see if they are easy to make out while going by in a car.
The DATES in big letters is also helpful.
When I go to garage sales, my method is to cruise the streets and follow the arrows. If I can't see the arrow in time to turn the corner, I missed the sale. Plus, it's hazardous to make an abrupt turn with someone on your tail!
I can't read one inch high pencilled words on a cardboard box!
It's also helpful to have all of one's signs be the same. Those trails are easier for me to follow, too!
(By the same, I mean, for examples, all the signs are hot pink with similar lettering, or on a paper plate, or the same size black on white)
Take the signs down when the sale is over!
Some sellers are willing to negotiate on the afternoon of the last day of the sale.
As far as negotiating/bargaining/haggling goes - that's up to you - you can put up signs saying that everything will be 1/2 price (except for maybe a few items) on the last day if you want -
if an item has a firm price on it, some sellers have the price and "firm" also on the tag.
I sometimes will ask a seller "Would you consider such and such" for an item. Some sellers will consider it - some won't.
Make sure items are clean. Get most of the dust off furniture, etc.
If you can hang garments, do so.
Also, if you could have a try-on area (that doesn't happen often, but it's awesome when it does!)
Group like items together.
Try to keep pairs of footwear together.
Have beverages for sale. Coffee if it's cold. Sodas, water, and juices if it's hot.
If this is a cash only sale, include that in the advertising and have it on a sign near the entrance of your sale.
Have helpers for the first few hours of the sale.
If you have a lot of stuff, perhaps rent a tent?
Some free stuff is good, too.
If you have pets, confine them. If you have very young children, make sure that they are accounted for, too.
Price tags - as a buyer, I want something that won't leave a mark when I try to remove it. As a seller, I would want something that would stay on the item until it is sold.
Also - be aware that some "buyers" will consider switching tags or try to tell you that the price is different from what you KNOW you put on it.
Parking - need a place to park and a way to get out!
If there are parking restrictions, make sure the shoppers know about them. Some areas don't allow on-street parking, or there's a fire hydrant, or one-side of the street only parking.
Have a back-up plan if the weather is "unfriendly"
Wear comfortable shoes.
Keep most of your cash "away" from the general traffic.