The Otogar is on the edge of city and has many major lines that come and go from Ankara and Istanbul all day long. Most of these lines will offer you a free service to the town square. There are also a few busses every day going every direction, to and from Izmir, Antalya, and Trabzon. To come and go from Samsun, the nearest city on the Black Sea coast, there are small Metro minibuses that leave several times a day.
Once you get a bus service or taxi to the town square, everything is within easy walking distance. If you are going on day trips to other villages in the region, you can find small privately-owned buses that come and go if you ask around.
For car rentals (if you're interested in a day trip to Hattusa, the Hittite capital, for example), there is a car rental/pet store very near the Train Station, and another near the bridge by Migros.
The major sights of the city include the whitewashed Ottoman houses lined by the river and the ancient Pontic rock tombs engraved on the side of the mountain overlooking the city.