I'll answer your question simply because you asked it, but I think cheating is horrible and its better to end a marriage than become an adulterer.
As for my answer, finding somone to have sex with isn't the hard part. I'm guessing you could find someone your wife, her friends, and her family don't know...you'll need to seriously lessen the risk that the other women will tell someone she knows and have your wife find out through the grapevine. Finding someone no one has met before just makes more sense than sleeping with your wife's best friend, you know? The biggest issue then will be keeping YOUR mouth shut. Obviously you won't be telling your wife, but you also can't tell YOUR friends, family, or anyone else. That just gives your wife more of a chance of finding out. Really, this entire ordeal is about finding someone no one knows and then keeping your mouth shut. If you can manage that, then you can successfully be a cheating as$h0le.