Before you start

For transport: an Ath.ena Ticket (anonymous reloadable) or a personalised Ath.ena Card for reduced/period fares
For driving on a non-EU licence: proof you've been a Greek resident for fewer than 6 months (after that you must exchange)
For a licence exchange: a Greek tax number (AFM) and registered residence address (proof of 185+ days / residency)

Step-by-step

1
Set up transit: get an Ath.ena Ticket/Card
Buy from any metro station machine or staffed counter. The integrated 90-minute ticket is €1.20 (€0.50 reduced) and covers metro Lines 1/2/3, buses, trolleys and tram on one validation. Anonymous Ath.ena Ticket loads single/period products; the personalised Ath.ena Card is required for reduced fares and is harder to lose. Day €4.10, 5-day €8.20, 30-day pass €27.
In personWho: YouMinutes at any stationTicket free to obtain; 90-min fare €1.20
2
Handle the airport leg separately
The standard 90-minute ticket does NOT cover the airport. Use the dedicated airport ticket: €9 one-way on metro Line 3 (or bus), €16 return, or €4.50 reduced. The X95 express bus to Syntagma is €5.50. The 3-day tourist ticket (€20) bundles a return airport trip — worth it for a short first stay.
In personWho: You~40 min metro to centre€9 one-way / €16 return airport
3
Decide if you even need to drive
Athens traffic and parking are punishing and the metro is expanding (Line 4 under construction; Line 3 already reaches the airport and Piraeus). For door-to-door, beige/yellow Athens taxis hail on the street or via the FREENOW app — Uber/Bolt in Athens dispatch licensed taxis through these apps, not private drivers. Scooter/moped sharing exists but mind aggressive traffic.
Mobile appWho: YouOn demandTaxi flagfall ~€1.50; FREENOW app-based
4
If driving: keep your EU licence, or exchange a non-EU one
EU/EEA licences are valid in Greece as-is — no exchange, indefinitely (you may exchange voluntarily). Non-EU holders may drive up to 6 months from establishing residency (carry an IDP if your licence isn't in Latin characters), then MUST exchange. Apply via the Regional Transport & Communications Directorate (book through gov.gr / a KEP). Reciprocal no-test exchange covers the USA, Canada, Australia, Japan, South Korea, South Africa, Switzerland, Serbia and a few others; everyone else sits the full Greek theory + practical exam at a driving school (σχολή οδηγών).
In personWho: YouExchange ~30–45 days; full test route weeks–monthsExchange ~€108 in fees + medical certs; full test route €600–1,000+

Documents you’ll need

Original valid foreign driving licence (+ official Greek translation for non-EU)
International Driving Permit if your licence isn't in Latin characters
Passport/ID and residence permit; proof of 185+ days residency
Greek tax number (AFM)
Two medical certificates (pathologist + ophthalmologist) for an exchange
Passport photo and a solemn declaration (υπεύθυνη δήλωση)

Things most newcomers don’t know

US, Canada and Australia DO convert without any driving test — contrary to common belief.

The official gov.gr/mitos service page lists the USA, Canada, Australia, Japan, South Korea and South Africa among reciprocal-exchange countries: ~€108 in fees, medical certs, no theory/practical exam. Many expat threads wrongly insist these nationalities must re-test, costing people needless driving-school fees.

Source: mitos.gov.gr (official) — USA/Canada/Australia/Japan/S.Korea/S.Africa conversion

The metro reaches the airport, so you rarely need a car or a pricey transfer.

Line 3 runs direct to Athens International for €9 one-way (€16 return). A taxi to the centre runs roughly €40 flat by day. The metro is also immune to the city's brutal surface traffic.

Source: OASA (official) + thisisathens.org

Ride-hail in Athens means licensed taxis, not private cars.

FREENOW is the dominant app and dispatches the official beige/yellow taxis; Uber operates only through this taxi channel. Expecting an UberX-style private driver leads to confusion — just use FREENOW or hail a street taxi.

Source: provider (FREENOW) consensus

Common mistakes to avoid

Using a normal 90-minute ticket for the airport — it's invalid there; you need the €9 airport ticket
Letting the 6-month non-EU grace period expire before exchanging — you're then driving unlicensed (insurance void)
Driving into the central daktylios ring (Mon–Thu 07:00–20:00, Fri to 15:00) on the wrong odd/even plate day — EVs, hybrids and LPG/CNG cars are exempt
Assuming you must re-sit the Greek test when your country (e.g. US/Canada/Australia) actually qualifies for a no-test exchange