Nothing prepares you for a bike tour like "time in the saddle." Even if you excel at other sports and consider yourself a strong athlete, you owe it to yourself to get a lot of riding in before your tour -- you use a lot of different muscles riding a bike. Also, when we're out on tours, we hear more people groaning about sore bums than sore muscles! Bottom line (sorry): ride more, and your butt will thank you later!
Here are some training tips.