The first burn is the most important. I recommend burning your candle for two hours for the first time as it’s important that the candle wax pools to the edges. Candle wax has memory which means if your candle doesn’t burn to the edges, it will create a tunnel effect and won’t burn evenly next time.
Trim your wick to ¼ inch and clear away the trimmings. Debris in the wax can cause the flame to flicker and lead to soot and blackening of the glass.
Keep the candle away from air streams like air conditioning vents, windows or fans for the same reason.