Flying is the fastest, easiest and cheapest way of getting to Greece from northern Europe. What's more, scheduled flights are so competitively priced that it's hardly worth hunting around for charter cheapies. Overland travel (buses and trains) between northern Europe and Greece is virtually a thing of the past. All too often, direct travel from this region is prohibitively expensive and difficult.
If you fancy arriving by water there are ferries to Patra from Trieste, Venice, Ancona, Bari and Brindisi, stopping at Corfu or Igoumenitsa on the way. In summer you can get ferries from Bari and Brindisi to Kefallonia.
Greece is an easy place to travel around thanks to a comprehensive public transport system. Buses are the mainstay of land transport, with a network that reaches out to the smallest villages. Trains are a good alternative, where available. To most visitors, though, travelling in Greece means island-hopping on the multitude of ferries that crisscross the Adriatic and the Aegean. If you're in a hurry, Greece also has an extensive domestic air network.