Athens is one of the most ancient cities in the world. As you walk its streets you will experience centuries of history passing you by. Magical constructions from another era, like the Acropolis, watch over modern life salted with traditional Greek customs.
Spring and autumn have wonderful weather, not too cold nor too hot and dry. Despite this you may want to visit in the winter for festivals such as the Feast of Saint Basil, or carnival. Easter is celebrated one week later than in the UK, and though many museums are archaeological sites are closed it is a chance to witness a traditional festivity.
Like many tourist centres Athens can attract pickpockets so consider leaving your valuables at home. A most important thing to remember is that small shops and restaurants do not accept credit cards, so get some cash when you arrive. Cost of living overall is lower than in London, so you needn't carry a lot of money with you. You can get a good meal for around €18 to €25. Souvlaki, a popular Greek fast food, is about €3.
From the airport to the city centre you can travel by metro, train, bus, or taxi. The cheapest is the express bus for about €5, and the most expensive, the taxi for around €35 during the day and €50 at night.
In Athens you can find accommodations for all budgets. Hostels, mainly in Plaka, offer shared rooms for about €10. Around the Acropolis region there are pensions and mid priced hotels. A practical, easy to move from place to stay is Syntagma square, and around it you can book 2 to 5 star hotels, according to your necessities. Despite the hot weather July and August are popular months to visit, so book your hotel ahead of time if you're travelling then. Once you have your room, leave your luggage and start exploring the city. Taxis are about €14 for a five km ride. Ask for the price of your ride before you get in and make sure the driver starts the meter. If you want to save for souvenirs buy a general ticket for public transport for about €1.20 for 70 minutes, a day ticket for around €4, and a 5 day ticket for approximately €10.