You may collect your tickets from designated port agents, located at the departure gates (where available) of the major ports (Piraeus, Rafina, Patras, Heraklion, Chania, Lavrio , Igoumenitsa etc) or close to the departure piers of the Islands ports, the latest 1 hour prior to the scheduled departure time.
Buy your ferry tickets from/to Piraeus, Serifos, Sifnos, Milos, Kimolos, Kythnos, Folegandros, Sikinos, Ios, Santorini (Thira or Thera), Anafi, Andros, Tinos, Mykonos, Syros, Paros, Naxos, Amorgos, Koufonissia, Heraklia, Schinousa, Donoussa, Rafina, Lavrio, Kea, Heraklio (Crete), Chania, Aghios Nikolaos, Sitia, Leros, Kasos, Karpathos, Tilos, Kalimnos, Kos, Rodos, Nysiros, Patmos, Kythira, Antikythira, Hydra, Spetses, Volos, Skopelos, Skiathos, Alonissos, Chios, Lesvos, Samos, Ikaria, Lemnos etc.
Also, from Venice, Ancona and Bari to Patras, Igoumenitsa, Corfu.