You can fly, you can go by train or you can take the car ferry. It all depends on what you prefer, how much luggage you'll have, how much time, and whether you want to start off in the parts that are near to England (e.g. Northern France) at one extreme, or jump straight to Italy.
Are you travelling to see Europe? If you are, I would suggest seeing it from a train or car if you have the time. If you're here for a number of time-dependent business meetings, you'll want to fly around.
