It's really quite simple...
First, go to the garage and dig out all the old books and games you've stashed away for the pending yard sale you're never going to have. Then, combine them with the books, games and CDs in the attic and the basement - the ones behind the boxes of baby clothes and your old sorority photo albums - and put everything in one room.
Now that the hard labor is over with...
List all your goods that you have to trade and all the goods you want to receive on swap.com, and leave the rest to us. We'll show you all the items you can receive for your items and the WA-LA! You start trading.
Once you find something you like click the "Get Now" link next to the item. A detailed description of both the item and the trader will appear so you can be certain it's what you want, and who you want to swap with. (Think 'online-dating-meets-eBay'.) When the other trader accepts your item the trade is complete, and you'll be provided with all the information necessary to ship your item.