When to go
May, June, and September are ideal — 75–85°F, the sea is warm enough, and you’ve missed the worst of summer crowds. July and August are hot (90s+), the Acropolis is brutal by noon, and the islands are jammed. October is still warm and ferry schedules are running. Winter (November–March) is mild (50s) and dirt cheap, but most islands shut down and ferry frequency drops.
Getting there
Emirates (via Newark), United (JFK), Delta (JFK seasonal), and American codeshares serve Athens. Nonstop is 9.5 hours eastbound, 10.5 westbound. From the airport (ATH), Metro Line 3 to Syntagma Square is €9 one-way and takes 40 minutes. Taxi flat-rate is €40 daytime, €55 night.
Visa & entry
Schengen — 90 days visa-free for US/UK/Australian/Canadian passports. Many travelers fly into Athens, do 2–3 days, then ferry to Santorini/Mykonos/Crete (those are still inside Schengen — no extra paperwork).
Money
Euro, ~€0.92 per USD. Cards work in hotels and bigger restaurants; cash needed for tavernas, kiosks, and some ferries. Tipping is light — round up or 5–10%. ATMs from Alpha Bank or Piraeus Bank are reliable; avoid the Euronet machines tourists flock to (terrible rates).
What to see
Three days in Athens is plenty: Acropolis at opening (8am, before tour buses arrive), Acropolis Museum, the Plaka neighborhood for dinner, the National Archaeological Museum (under-visited, world-class), and a day at Cape Sounion for the Temple of Poseidon at sunset. Then ferry to an island for 4–6 days — Santorini and Mykonos are famous and expensive, Naxos and Milos are quieter and cheaper, Crete combines ruins and beach.