Most places in Turkey are connected by bus. Even small towns will have a Otogar, or bus station with regular services running all over the country. There are some places though, that you may want to see, that have irregular or limited bus service. In this case, you may consider hiring a car.
Here are a few points to consider.
Turkey has one of the highest, if not the highest petrol price in the world. You often pay more than 5 Lira per litre for petrol. You should understand that renting a car is not the most economical way to get around. Petrol stations are abundant on major roads, you should have no problems finding one. They are all full service. They seem to prefer cash to credit card as well, so you should keep that in mind.
Most rental cars have a manual transmission, so if you are coming from North America and are used to driving an automatic car, make sure you request one in Turkey. Otherwise, you may be in for a shock when you get the car!
Turkey drives on the right and has standard European road signs. Signs that are written will be in Turkish only. This should not present a major issue though, as most signs use pictures instead of being written.
Highways have lanes just like in other countries, but you are unlikely to see Turkish people use them! Driving between two lanes is very common and driving on the shoulder is considered normal, especially when making a right turn. Overtaking on the right, while illegal, is very common.
You should drive defensively. Cars will often join the road without checking if the lane is clear. If you think a driver has not seen you, sound you horn, flash you lights, or both. Be aware that most drivers will not indicate before they change lanes or overtake you.
Overall though, once you get used to how the Turks drive, you should be fine; but don’t expect a leasurely afternoon drive through the countryside!