The essential ingredient of candle is wick as the wax burns according to the wick used in candles. Thus great precautions should be observed while choosing wick. Wick can be categorized as:

Floating Wick: Special wick for floating candles give excellent result.
T-lite wick: used in T-lite.
Gel Wick: Used for making gell candles of various sizes container
Pillar wick: As per the diameter of the candle thread is used. It is available in many sizes

 There is no hard and fast rule for selecting wick size. The choice of wick size and type largely depends on the judgment and experience .