The city center is easily accesible by foot. Other options are bicycle and car. There is a public transportation net but not very good.
Get a spa at apelviken or just walk around... Varberg also has some of the best wind surfing in Sweden.
Varberg has several different restaurants and bars serving food. It also has a fish shop in the harbour for those wanting to make their own meal.
Varberg has several bars and a good nightlife in the summer. Most bars are open to 2am on the weekends.