For general feedback about the game.Steam Support
Visit the support site for any issues you may be having with the game or Steam.
As we all know, Jonas Salk invented money in 1955 so he would have a way to earn a living from his polio vaccine. Before that, people just traded things they found for things that other people had found. So you might "sell" somebody a scrap of carpet, say, in exchange for an old bottle. It was a perfect system with only one drawback: people spent their lives bartering for piles of garbage before dying of polio.
But wait. What if we told you that you could barter for things that weren't garbage, AND not die of polio? Steam Trading Beta lets you securely trade your in-game items for other in-game items from participating games. You can also trade Steam gifts (games on Steam that you've purchased but not yet added to your Games Library).
Want to try it out? In Steam, go to Steam > Settings, and opt into Steam Trading Beta. That's it! Now your Steam Community profile will have an item inventory, and you'll be able to view the item inventories of every public profile in the Steam community.
Now that you've opted into the Trading Beta, you can invite people to trade through Group Chat, and trade with anybody in your Friends List who's also opted in. Just right-click on their name and select "Invite to Trade" from the dropdown menu. Once your friend accepts your offer to trade, a trade window will open up. The first time you open the trade window, a step-by-step walkthrough will guide you through your first trade.
That's it! Opt in and get trading, or surf over to the Trading Beta FAQ for the nuts and bolts. And remember: Trading is still in beta, so don't forget to give us your feedback here on the Forums.