Wax has a memory and will not burn past what it burned previously. So, if you don't melt across the full diameter of the candle the first time, the wax will not burn beyond that point. To avoid this the general rule of thumb is for every inch in diameter you should burn your candle for one hour. So for example a three inch candle should burn for three hours to achieve an even burn across the diameter of the candle. This also ensures the best scent throw from your candle, and will help to prevent future tunneling.
Do Not burn your candle for more than 4 hours in one go. Never extinguish your candle by blowing on the flame, always use a snuffer.
To ensure the best burn from your candle, you should keep the wick trimmed to around 1cm in height. This is so you get the cleanest burn possible as leaving your wick untrimmed leaves your wick laden with soot that can cause smoke. Use a snuffer to extinguish the flame and when cool trim to approximately 1cm in height.
To reduce tunneling in your candle always ensure you have an equal burn pool across the diameter of the candle when burning. The general rule of thumb is one hour burn time for each inch in diameter of the candle. Never leave a burning candle unattended.
If tunneling has already occurred place a piece of foil around the outside and fold it over the top, leaving a hole for the flame to get oxygen. Leave for around 30 minutes and the excess wax should have melted off the sides. Alternatively, place the candle in a hurricane jar.
You should use a 4 hour burn, non scented tea light candle in a wax melt burner.