For oolong tea it is the soil and the climate that play a big part in determining the final product. The best of Oolong Tea comes from Taiwan.

After plucking the leaves are first withered in the sun, then inside at room temperature. As this is a slow process an oxidation (fermentation) gets started, turning the leaves red and developing the characteristic fragrance. This process is stopped in pan firing a first time.
The leaves are then rolled and fired a second time. After which they are rolled again and fired for a final time.

Most of the tea growers use nowadays electric pans; we found a 4th generation tea-grower that is is still pan-firing in the traditional way, above a coal fire.