From Olbia

The easiest way to get there goes through Luogosanto.
If you follow the route on the map you will drive from Olbia, Arzachena, Luogosanto, Aglientu and Costa Paradiso.
As you pass Santa Teresa you will find Vignola, then you will drive for another 10 km and you will find a sign on the right for Costa Paradiso.

However the most beautiful route is the one that goes through Tempio Pausania and the so-called Limbara mountains.

It is a winding road but very picturesque. You go through Olbia, Tempio, Aggius, Trinità D'Agultu, then you turn for Santa Teresa and after 15 km you will find Costa Paradiso on your left.

Note: Note that there are two more ways to get there from Olbia, but they are quite complicated and not suitable for first time visitors.

From Alghero and Porto Torres

If you are coming from Alghero or from Porto Torres you have to drive towards Castelsardo and then take the fast road to Santa Teresa di Gallura. If you come from Alghero you have to go to Sassari first.