Make sure to trim your candle wick after and before every burn. It should be less than 0.25 inches, but not too short. The best way to do this is using a wick trimmer, like this brass wick trimmer from CB2. It’s good practice to burn your candle until the whole surface is a liquid, that way you’ll get an even burn the whole way through and your candle won’t tunnel down, making it harder to light.