When you light your candle for the first time it is best to let it burn for a couple of hours until the whole top of the candle is a melted wax pool. This will insure that when you light your candle the next time that it will burn down the sides of your jar leaving minimal wax behind.
Keep your wick trimmed to 1/4 inch. When you cut the burned wick off do not leave it in the candle wax.
Use a Wick Dipper to extinguish your candle. Not only will your nicely fragrant room continue to smell nice, (and not like a blown out candle) but when you dip the burning wick in to the melted pool of wax, it moistens and re waxes the wick for the next time.