Most overseas visitors touch down at Malata International Airport, about 20 minutes from Valletta by car.
Boats
There are ferries from nearby east-coast towns, but you'll probably use those for exploring rather than arriving. If you're coming from Sicily, there's a boat service that'll bring you to Valletta.
Automobiles
Driving in Valletta is a challenge — it's an historic city with lots of one-way streets and pedestrian zones, and not much parking.