Put a price tag on it. Successful bartering must result in the satisfaction of both parties. This can only happen if the items bartered are realistically valued. If you have an item you would like to trade, obtain an accurate appraisal. An item is only worth what someone is willing to pay for it. Therefore, do your research and look at the "selling" section on eBay to find out what online buyers have paid for similar items.

For one thing, the barter myth “makes it possible to imagine a world that is nothing more than a series of cold-blooded calculations,” writes Graeber in Debt. This view is quite common now, even when behavioral economists have made a convincing case that humans are much more complicated—and less rational—than classical economic models would suggest.
Barter is the process of trading products, goods or services, for other products, goods or services. It is a simple method of transaction, frequently one in which no money is exchanged. Barter systems are often utilized between nations, and sometimes between a nation and a corporation. Barter also occurs between corporations or companies and other businesses, and sometimes between a business and an individual, or two individuals. In the United States, billions of dollars worth of goods and services are exchanged each year through bartering.
An online community in which you can either share free stuff or rent items for a fee, NeighborhoodGoods bills itself as a “social inventory,” enabling members to save money and resources by borrowing what they need to use. While joining is free of charge, you can create private sharing groups for your business or neighborhood for a small fee: $36 for six months.
So as you consider items to stockpile, you should think about items that are necessary, but might not take up a lot of space.  Referring back to Mark Goodwin’s book mentioned above, one thing the main characters looked for were canning lids and rings.  They don’t take up a lot of space and in a real collapse situation, they will be really worth it!
In a small economy where individuals specialize in trades, they may find the process of setting up a centralized currency and maintaining it an unnecessary burden in order to trade. One option may be to use a commodity to exchange value between parties that want to trade goods or services and this is why gold and silver have been useful forms of currency in many cultures and times. Another option may be to use a barter system to trade.
But various anthropologists have pointed out that this barter economy has never been witnessed as researchers have traveled to undeveloped parts of the globe. “No example of a barter economy, pure and simple, has ever been described, let alone the emergence from it of money,” wrote the Cambridge anthropology professor Caroline Humphrey in a 1985 paper. “All available ethnography suggests that there never has been such a thing.”