Thessaly : Karditsa
Karditsa is a city in Thessaly.
The closest airport is Volos airport  (VOL), situated in (Nea Anchialos), about 95 km W from the city. There is a bus connecting airport and Volos bus station. Buses are waiting to pick up travelers after a plane lands, the cost form the airport to Volos Bus station is 3 €. Then you have to get another bus or Train from Volos to Trikala.
By regional coach
Interurban coaches ("KTEL" buses) are by far the most convenient way to travel around Greece, as well as for intra-regional travelling. There is frequent bus service from Athens Liossion Station to Karditsa, as well as from Thessaloniki bus terminal "Macedonia" to Karditsa.
Trains (OSE) connect Karditsa to other cities in Greece. Travelling with ordinary trains can be cheaper, although a little bit slower, whereas choosing a fancy faster Intercity train will cost the same amount of money, or even more than a KTEL bus.