DISCLAIMER: Consult the appropriate laws on the collection of goods and materials from government-owned public lands, whether the lands are federal, state, or municipally owned.
There are often laws pertaining to the commercial use of these lands, and the taking and/or use of wild animals, plants, and minerals or their parts may be restricted or forbidden. Vehicle access may also be restricted to certain areas. You can be fined or possibly even arrested for the violation of these laws, so conduct research on the laws BEFORE you enter these lands.
There are thousands of different things that you can find while you are outside doing yard work, recreating, or bee-bopping around in your ORV, snowmobile, or vehicle that you can quickly and easily sell. While you are out having fun, you might as well try to pay for the gas you put in the gas tank to get you out there, right?
Before you leave your house, you should prepare for locating items to sell. Put together a ‘gathering kit’ that you can bring with you, whether you are in a car or on a smaller recreational vehicle. Find a small gear bag or backpack that is the right size for you to carry, and does not get in the way of the other activities that you got you outside in the first place.
Inside the bag, you will need a lightweight set of tools that you will use often while gathering items to sell. You will want to tailor your set to the types of items that you like to sell. Make sure that you have plenty of room left over inside the bag to place items when you find them.
At the minimum, I would recommend including the following items: Work gloves, bug spray, a small first aid kit, a small magnet, a multi-tool (Leatherman-type) that has both types of screwdrivers, a knife, needle-nose pliers, and a wire cutter; several additional rolled bags i.e. garbage bags or burlap sacks to put stuff in, a map of the area you are exploring, a compass, a cellular telephone, pencil and paper, and this handy-dandy book for reference.
If you have a handheld GPS or smart-phone that has GPS capabilities, you are ahead of the game. You can mark locations to return to, and easily find your way back to your vehicle if you are out on foot.
OK, so after you are mobile, what are you looking for? Basically anything that people might want to use, or that you can find value in. You have already done part of your research by reading this book. You have an excellent selection of items to look for.
Now, just start thinking logically while you are out having fun. When you see things in the woods, either collect them, or write them down on your pad of paper to check when you get home.
When I started this gig, I sat down in front of a computer and just started searching for things that I could possibly find in the woods in my area. I did searches on EBay completed items and Google searches for items I was seeing while hunting, fishing, or whatever else got me outside. Some items were worth gathering, and some were not. Some items I immediately found that I could sell on eBay, some took more digging to find places to sell them.