Today the grass skirts and loin cloths have all but vanished as many ethnic Fijians wear a piece of cloth around their waist called a sulu. This is worn by both men and women and it can come in various patterns and styles. It is most common in the villages, but there are sulus appropriate for business to match suits and the military also has a sulu that is a part of their ceremonial uniform.
In addition to the sulu the clothing is quite varied depending on the situation and individual. In the cities western-styled shirts or blouses are common as are suit jackets for formal occasions. In towns and villages more traditional tops are more common, including many made from local materials. However, throughout Fiji the people are somewhat conservative and showing too much skin is odd if not offensive and the locals won't be wearing short pants or skirts and you won't see exposed shoulders either.
With a large Indian population in Fiji it is also common to see traditional clothing from India, especially among the women. This generally includes brightly colored sarongs or similar items. Like the Fijians, the Indians cover up and always wear long pants and shirts.
As a visitor to Fiji there are two types of clothing that can be worn. The first is in your hotel or resort (as long as your resort specifically caters to foreigners), where swimsuits, shorts, and tank tops are acceptable. The second is whenever you are outside your hotel or resort. Shorts or skirts are considered inappropriate (unless they reach beyond your knees) as is showing your shoulders (and for women even showing your elbows). Because of the climate in Fiji this becomes a challenge so many visitors buy a sulu upon arrival and wear it over their shorts or skirt. For tops, try to wear light and loose fitting shirts that extend beyond your elbows. Also, if ever in a village, never wear a hat as this is offensive to the chief.