How could you play a Yu-Gi-Oh duel online

Answer! If your talking about going online on a Yu-Gi-Oh! DS game such as "Spirit Caller" or "World Tournament 2007," I suggust going here to get your answer: http://www.nintendowifi.com/consumerservice/showFAQCategory.do I hope this help you.

*Using a standard computer with an internet connection, there are a variety of ways to duel other people online using free programs. The best of these in my opinion is YVD 8.6. That stands for Yu-Gi-Oh Virtual Desktop. It lets you use any cards to make any deck and duel other people online. The community is pretty good, and new cards are added withing a month or so of their real life releases. It does take a tiny bit of getting used to, and the new card pictures have to be moved to the correct folder manually, but I find it to be very good. -Dragonheart91*

This is another place you can duel online: http://yugiohnetwork.com , it's webbased and you won't need to download anything. Currently, it has English version.