If you are an avid candle user a wick trimmer is a must to take good care and get the most of your candles.
 
WHY DO YOU NEED TO TRIM YOUR WICKS?
It's important for so many reasons but let's name a few; 
Clean burn: avoid dark smoke (and smoke alarm detector!)
Clean container: avoid smoky candle jars
Better fragrance diffusion: enhance the scent diffusion while burning 
Burn safely: a longer wick creates a higher flame which can be dangerous
Prevent mushrooming: remove the build-up of carbon
 
HOW (AND HOW OFTEN) DO YOU USE A WICK TRIMMER? 
Good news, it’s quick and simple! But it's a routine and you have to do it, every-time you use your candles. 
Place the wick trimmer handle inside the rim of the jar 
Bring the blades towards the wick parallel to the wax
Cut the wick to a height of about 4/5 mm
Throw the wick debris