KTEL provides very convenient bus service on the Santorini island. Bus is non-smoking, clean and comfortable.
For the time we were there, mid-May 2008, bus schedules of all services were posted at the booth at the bus station at Fira (also somewhere at Oia bus station). Free xerox copy was distributed upon request (if not, you can take a digital picture of the posted schedule with your camera or mobile phone).
Apparently the bus schedule changes often, each schedule print out has valid dates on it.
Service between Fira and Oia is frequent (see photo).
To have the fun of mass confusion, several buses to different destinations leave Fira bus station at the exact same time. Make sure that you are actually on the very bus heading to Oia!
The sunset (total set) in mid-May is right before 20:30, the last bus leaving Oia was 21:35, which would be good for people want to experience the sunset in Oia and return to other hotels in other places on the island.
We could only imagine how crowded the last bus would be (there was an army of people in Oia waiting for the sunset when we left with 19:15 bus). You can always opt to take a taxi (not expensive, but not use meter) or other modes back to hotel.
There are few stops in Oia but there is only one bus station. Direct buses run usually only from Fira. There are no direct buses from the port or airport. If you wish to get from those places you need to take a taxi and it will cost about 20 - 25 Euro. Most hotels organize also their own transfers and it may be a good option.
The bus fare in 2007 from Fira to Oia was 1,20 Euro. Buses run every half an hour until about midnight.
Ferries in Greece is almost always late. The one in Mykonos which will take me to Santorini was delayed by an hour. To make matters worse, there was a sand storm that stings your eyes and the sand gets into everything even your ears!
It's better to wait at your hotel (if it is near the port) and have them call the port periodically to see if the ferry has arrived. Also, take the speed boat to Santorini which will take 3 hours to get there unless you want to plod along.
As you are about to reach Santorini, get your cameras ready. The view is to die for!
Oia is small enough to explore by foot. But if you want to go around Santorini and see what's on the other side, easiest way is to rent a small car as the roads are narrow and windy.
I love my little SMART car by Mercedes Benz with couples only seating. It's the luxury version of Kancil (local car in Malaysia)
When travelling from Oia back to Fira, try and hurry after the sun goes down to get to the buses. I didn't & had to catch the last bus. It was absolutely packed with people having to stand in the aisles and stairwells.
In May, there are not many tourists, and then few cars. I rented a scooter and had a great time. If you never drived one, forget it, and rent a quad (rather expensive, 20€, like a small car), which is safer (4 wheels)
Oia is situated on the extreme northwest tip of the island, quite far from the port. Getting there is a bit, shall we say, interesting, because you have to travel on a very windy road clutching the edge of steep cliffs. The bus trip to Oia can be downright terrifying, so I'm glad we took a taxi there and then took the bus back after dark when we couldn't see how close we were to the edge.