The times of the shuttles from the Dalaman airport to Marmaris are arranged according to the landing times of domestic lines planes. The shuttles of Havas from Dalaman to Marmaris leave from the Dalaman Airport 25 minutes after aircraft landing times.
If you have booked your holiday through a tour operator they will arrange your transfer to your hotel. Otherwise, your transportation options from the airport will be taxi and shuttle (called “Havasâ€) which leave Dalaman Airport every 2-3 hours and cost around 25 Turkish Lira ($12).
I have been to Marmaris a couple of times. It's a fantastic place. The best beach there is in Icemeler and the nightlife is down bar street. One of my highlights in Marmaris was visiting the Bazaar and also doing a Gullet boat trip. You can arrange one from the marina. There is also a water-park on the road to Icemeler which is good fun.