It is a good idea to agree the fare before you set off.
Went to Turkey last year but we paid, via the agent, for our transfer which was as it turned out just in a taxi.
He was really good, explaining about the sights we were passing, he even stopped at a shop....we thought so he could get himself a drink, but he gave us each a bottle of water! He also stopped at a beautiful spot overlooking the sea so we could take photos.....of course after this we tipped him!
Going back though he was 1 hour late picking us up for the airport (early morning) and didn't arrive until after we'd called the local rep. However he was so apologetic, he'd obviously overslept!