Make sure the motorcycle has the proper registration. You can obtain registration for your motorcycle at your state Department of Motor Vehicles.
Purchase a train ticket for the motorcycle. For the train company TGV-Europe, ticket prices in 2009 start at about $75 US.
Arranged for pick up of your motorcycle. Train companies such as TGV-Europe will pick up the motorcycle for departure or you can park the motorcycle at the specified train station before departure and TGV-Europe will put it on the train--free of charge.
Take another form of transportation (plane, commuter train) while your motorcycle is en route to your destination.