There's no train connection with Dalaman Airport.
Car and bus
Dalaman Airport is easily accessible by rental car. Freeway D400 running north of the airport connects the tourist resorts east and west of the airport. The exit to the airport is clearly signposted.
There are no regular bus services but there's a Havas shuttle bus (Tel. +90(0)252 444 0487) to Marmaris and Fethiye.
Car rental Dalaman Airport
You can find counters of car rental companies in the Arrivals Hall. Three rental companies are present at Dalaman Airport: Avis, Budget and Europcar. You can also book a rental car in advance using the service provided by EasyTerra; they compare the rates of several providers in a single quote.
There are taxis outside the Arrivals Hall. The (set) rates for various destinations are indicated on a sign, but this doesn't mean that a driver keeps to it. Therefore make sure to agree on a price upfront.
There's a parking lot outside the terminal with places for almost 800 cars.