As you can see from the map of Delphi the site is quite a distance from other ancient sites. If you’re staying in Athens you can get to Delphi by booking a coach tour. It’s best to get information from your hotel or local travel agent. They are usually day trips, and give you enough time to see the sites and the museum. Check if they include lunch and a tour guide. Some of them have lunch provided as an extra, I’m not sure it’s a good idea as there are quite a few tavernas and restaurants in the town. A tour guide can be useful if you prefer to be looked after. If you’re a more independent type you might rather to go around at your own pace with a good guide book.
Don’t forget that the sites are about 500m from the town itself.
You can also travel by bus from the bus terminal in Athens. This is much cheaper, and gives you more time at the site. You go to Terminal B, which is on 260 Liossion Street. This is about 5km from Syntagma, and you can get there by bus from Amalias Ave by Syntagma Square or Panapistimiou street, or by taxi which shouldn’t cost more than about €10–though last time I had to argue this with the driver. Check beforehand for departures, and make sure you get there in good time.
If you are traveling by car there are a good number of hotels and guest houses. There’s a plentiful supply of budget hotels, quite a few mid range ones, and a couple of posh ones.
Map of Delphi
This map shows you where the site is in relation to Athens (just hover your mouse over the red markers). You can use the controls on the left to zoom in and out of the map, and you can move the map around by holding down your mouse button and moving the mouse around. The “Satellite” view is quite good, and if you zoom in on the site you can clearly see the stadium, theatre, temple, and even the tholos at the Sanctuary of Athena.