I arrived by train, and I chose to stay near the train station. That worked well for us, as it is not the greatest of the experiences to be carrying your luggage into the vaporetos and across the steep bridges.
If you are arriving by plane, I believe there are buses that takes you to Piazzale Roma. From there it is jus a very short walk to the "People Mover" monorail station, which takes you to the msc checkin terminal.
Hope this helps.