Carbon steel woks are the most common type used due to their ability to evenly distribute heat and high conductivity, and it is important to properly clean and season a new one prior to use. Non-stick and electric woks do not require seasoning, however, they are not recommended because they do not provide the high heat required for stir-frying, and the non-stick coating may wear out over time.
Seasoning a wok prevents food from sticking, discoloring or imparting a metallic taste by creating a smooth cooking surface. Thoroughly scrub your wok with dish detergent and a scouring pad, then rinse. Set over high heat, rub one or two tablespoons of cooking oil all the over the inside of the wok with a folded paper towel, and continue heating for about 30 seconds. Let cool, then rinse with warm water. Repeat the oiling process until the paper towel comes out clean, about 3 times. Your wok is now ready for cooking.
My mother-in-law, who is from Hong Kong, recommends using a chunk of pork fat and a few stalks of Chinese chives for the seasoning process, rather than plain cooking oil. Using this method breaks in the wok using food, rather than just oil, and the strong aroma in the chives helps to reduce the metallic-y flavor a new wok might transfer to food during cooking.
Seasoning a wok is painstaking, but required in order to properly prepare the wok for use. Over time, the bottom of the wok will develop a black patina, which provides a natural non-stick surface and adds that distinctive stir fried flavor to foods. After each use, scrub off all food particles with a brush under warm water, dry off excess water with a cloth towel, heat on the stove to evaporate any remaining moisture, and rub a small amount of oil on the bottom and sides. If any rust develops, scrub it off with a scouring pad, and re-season the wok. Maintaining your wok in this manner will keep it in top shape and provide you with a lifetime of use.