Light: floral (Tieguanyin green style, high-mountain). Heavy: roasted (Da Hong Pao, dark Tieguanyin) Oolong spans green-like to black-like teas, so this matters more than the label.
Origin
Taiwan (Alishan, Dong Ding) or Fujian (Anxi, Wuyi), stated on the pack Origin defines the style.
Brewing
About 85 to 95°C; works for repeated short steeps Good oolong gives several infusions.
Brands that matter
Rishi: Good loose oolongs.
Harney & Sons: Accessible oolongs, including Formosa.