Trim wick to approximately inch after each use. At this point, wick dippers can be used to reposition the wick in the center of the candle. Occasionally the wick will shift inside the wax pool. To keep your candle looking clean, you should wipe any excess black smoke that may form around your candle after each use.
Black smoke is cause when too much wind hits the flame.
When your candle is finished, you may freeze the candle jar in a refrigerator to help remove the excess wax left over. When the wax is cold enough it should easily scrape right out.