Why do you emphasize trimming the wick?

Trimming the wick is the most important part of taking care of your candle. Think of it as a pump and the liquid wax as the fuel to be pumped. If the wick is too short you get a very small flame until more wick is exposed. If the wick is too long the flame is too large causing smoking and the wax pool to become too large too fast. This is particulary important with pillar candles as too large a flame will cause excessive dripping.