1. On the first burn make sure your wick is trimmed to 1/4", allow the wax to fully melt to the edge of the vessel (2-3 hours). This will help prevent tunneling and extend the life of your candle!  
2. On every new burn, re-trim the wick to 1/4." the shorter the wick the longer and cleaner burn time you will have. There should never be carbon build up on your wick, this is was creates a large flame and black smoke. 
3. Do NOT burn the candle for longer than 3-4 hours at a time. it's time for a refill when there is 1/4" wax remaining. 
4. Keep your candle free of debris and soot buildup. if you notice black soot buildup around the edge of your vessel, its time to clean it. this can simply be done with warm water and a paper towel. 
5. Do NOT ever move a burning candle. before you move it blow it out and allow the wax to cool.

Troubleshooting 

Tunneling: use the tinfoil trick found on youtube 

Lost wick: simply use a butterknife to take out the wax that is over the wick