I always buy scented candles based on their fragrance. I have learned over time to smell the lid of a candle if it is in a container rather than the candle itself. The fragrance of a candle is trapped in the lid over a period of time when it is enclosed. When you smell the scented candle itself you are only smelling the top note. When you smell the lid you get the top, middle and base note.
This is similar to win tasting where people will swill a glass of wine when before they taste it. People well swill the glass of wine in it to get the top, middle and base note of the wine.
I always light a candle 15-30 minutes before an event in order to set the scene. This is because the smell of the candle comes from the candle wax which forms at the base of a candle when it is lit. It is important to light a candle for 15-30 minutes to get that smell.
I have learned from experience to not use candle warmers with candles. They will drive the smell out of candles over a period of time. As we have seen the scent from a candle comes from the liquid candle wax at the base of the candle. This will work fine when you light a candle the first or second time. However after that the warming effect on the rest of the candle will have driven the fragrance out of the candle.
I hate the sight of soot from a candle. You can stop soot by keeping the wick a quarter of an inch from the top every time you light it. If the wick is over a quart of an inch it will only burn soot and not the candle benath it. Goog quality candles from reputable companies tend to have less soot. A lumo cover over the candle is good for airflow and stopping soot from the candle.
A candle will burn longer if you keep lighting it. This is because wax will form on the side of a candle and solidify the more you light it. This will then have to be burned off.