If you haven't already, start decluttering your home. Prep for a yard sale.
And scope out ones in your area. Only buy what is needed but look for some good deals. If you are a re-seller look for items that can be easily mended or repaired and resold for a profit.
To save on gas look in the local paper for a list and address of yard sales, map out your route.
Leave Early. Go late. Early birds get the worm. But if you go by them as they are closing up the sale, items go for alot less. Many just want the stuff gone and do not want to pack it back up.. I have gotten a lot of free stuff that way!
Don't be afraid to negotiate prices
Carry small bills
Scope out each sale before shopping. This way if you see must have, you can grab it before someone walks by with it. For large items you are for sure you want, settle that purchase with the seller then continue shopping.
Bring the reusable shopping bags with you. Makes holding all your finds easier.