An hour or so from the ferry port is Senggigi - a simple white beach and a range of expensive hotels.  There are a few backpacking places of average quality but there are better places on the island.  However, it's a pleasant enough town and a good place to treat yourself after any tough journeys you've had.  And the sunsets over Gunung Agung on Bali are pretty stunning.

This massive volcano (nearly 4000m) dominates the northern part of the island and was considered dormant until 1994 when it proved otherwise.  Trekking at least part of the way up Rinjani is the reason many tourists come to Lombok and most base themselves in the nearby villages of Senaru and Batu Koq or in the foothills at tiny Tetebatu.

The Sasak people of this area are known for their weaving and dancing; however, one of the most entertaining events is the stickfighting contests which involve two young men beating the hell out of each other with the help of big sticks and shields.

But what you really should be doing is climbing Rinjani.  You have several choices and a couple of starting points.  The most popular is from Senaru where a steep day climb will take you to an incredible stop overlooking the massive caldera containing a crater lake and perfect volcanic cone.  

A longer three to four day trek will take you into the caldera and to the hot springs; it will also involve the incredibly tough climb to the highest point on the rim - a scramble up volcanic scree with a five thousand feet (1500m) drop on one side and not much else on the other.  It is a relentless journey but a fantastic achievement.