When it comes to public transport inside Forssa there is only Tyykikyyti which is a call based type of service. Luckily Forssa is small enough so you can basically walk or take a short cycle everywhere you need to go in the city.
Bicycle might be you best purchase unless you live right in the middle of Forssa. Even if your bicycle breaks down there’s a great repair shop at a local sporting goods store Urheilu-Kenni. They take great care of you bike and do it with a very small cost by Finnish standards.
Public transport in and out Forssa is a bit better than public transport inside Forssa. Bus is you best option if you want to go to Turku, Helsinki, Pori or Lahti. There’s a bus leaving to or arriving from each of these cities at least once an hour. Bus companies that offer these services are Onnibus and Matkahuolto. Bus tickets are sold online or by the bus driver. The bus station is to the north from the city square. Busses don’t travel that much during the night so if you are planning to go party in bigger cities you might want to get a room from there.
The nearest train station is in Humppila 23km and the train takes you only to Tampere or Turku from there. Another train station is in Hämeenlinna 50km away and from there you can go to Helsinki or Tampere. Of these stations Humppila is the smaller one so finding a ride there or a train from there might be harder to come by.