well i have actually only done this once myself, currently i participate in sevearal group garage sales throughput the year where i don't have to actualy do it all myself but some tips that might help:
~price each item that you are going to sell, pricing by table is tough to keep track of
~half of a file card and a straight pin work great for listing prices on clothing and you can tape the cards to most other objects
~if it's a large sale seperate things by department, and clothing by size and hang clothing if possible
~advertise, here's the key to a great sale
~make sure you have lots of change and bags on hand
~if you are willing to negotiate prices make a large sign and let ppl know, a lot of ppl won't haggle if they feel insecure about it and will jsut leave without buying whatever teh item was
~same is true if you are planning on a half priced day at teh end of the sale, it won't keep ppl from coming the first day, they want to get items befoe someone else but it will bring buyers in even if most of the stuff is gone, but you must include this in your ad
~may sound strange but make sure teh area you are having teh sale is well lit and clean, try to eliminate any items taht aren't for sale and have plenty of space for teh items you are selling, ppl won't stop if it doesn't look like you have something good when they drive by
~and ensure parking as best as you can
hope some of this helps, good luck