Remember to trim the wick to 1/4" and don't burn more than a few hours before trimming and relighting. This will increase your burn time and help prevent smoke and overheating that can cause the candle to crack or combust.
Place candles on a hard, flat surface or tray that will not be damaged by heat, flame, smoke and/or if the bowl breaks and the wax leaks or spills.
Do not burn candles near furniture, drapes, carpet, paper or anything that could catch fire or be damaged if the candle cracks or breaks due to heat, smokes or catches fire.