Keeping their wicks trimmed properly will help your candles burn fully and last longer. Your candle's wick should be trimmed after every 4 hours of burn time. Let the candle come to room temperature, then trim the wick before relighting. Trimming wick to 1/8 inch helps create complete combustion, which means less soot is formed while the candle is burning.
Tips From Me to You:
If you love candles, you need a wick trimmer its good for your candle - trimming your candle is important as using either your fingers or scissors can cause your candle to burn lopsided or make it tunnel.