Buses are going to suburbs and villages and its ticket is from 1 euro to 3 euros. It depends in which place you go.
Tram has got two routes and it ain't too expensive. About 1,30 Euro you can buy a ticket.
Taxi is quite expensive! So I advise you that you don't look for a taxi. It's better to ride with a tram or a bus. Even on foot you can cross the whole town within 2 hours(from end to an end). Just get a map in Tourist Center and everything will be ok.