If you have a car, go east along Daxue Road, and you will find the national highway 104. Turn right and walk south for half an hour to get to Taian. Maybe the coach will go this way, too.
Wait for the bus at National Highway 104, and get on when you see someone passing by Tai 'anzu. 10 yuan is fine, don't give more, and so on. There are many buses to Tai 'an.