Oolong is a big grouping and includes teas from different areas, so covering them all in one column would be impossible. Further complicating the subject is the sheer number of steps in the production process.
Unlike with other teas, such as longjing, which farmers make with the youngest leaves (those at the tips of the plant), oolongs are generally made with the second and third leaves down, which are young but half or almost fully open. The broader leaf allows oxidisation to take place on the edges first and spread inward gradually, creating an intricate profile of aromas and flavours, ranging from flowery to fruity, and with a bittersweet or sweet aftertaste.
After they're picked, leaves undergo a withering process, either in the sun or indoors in a temperature-controlled room. This step helps to demoisturise the leaves and soften them, as well as destroy chlorophyll and so remove undesirable grassiness. Once they are withered, they are allowed to cool off and the remaining moisture distributes itself evenly.
The next step is the "rattling" (or shaking together) of the withered leaves - either by machine or by hand. As they rub against each other, they become bruised, which helps further the oxidisation of the polyphenols in the tea; the moisture is also reduced further, adding to the aroma of the final product. Rattling is essentially what gives oolong leaves their defining colours: green, with red/brown rims.
Once a tea farmer has determined that his leaves have been properly prepared (a process that takes between eight and 10 hours), they are fired for the first time. The high temperature stops any more oxidisation by destroying the enzymes in the leaves. This process also helps to define the taste of a tea; it is a bit like frying vegetables without oil - the freshness and essence of the leaves are preserved.
