If you want to maximize the life and enjoyment of your candles
(not to mention ensure safe habits) it is important to note that there are a few must do's when it comes to burning candles.  If the candle is a *quality product, you should be able to rely on a few basic rules.  Not only will you avoid frustrating occurrences like spills or having to dig wicks out, you will keep your setting safe.  

Note*Be sure to read each individual candles instructions since there are a wide variety of candles made.

Generally...

#1 Never ever leave a burning candle unattended.

The time frame per instance you burn a candle is determined by the diameter of the candle SO...

#2 Every time you burn a candle, burn it one hour per one inch in diameter or  until the melting wax is approaching the edge of the candle.
ie. a 3 inch diameter =3 hours ( this is an approximate approach).
You will save yourself the frustration of spills (a result of over burning) and having to dig a wick out of wax (  problem of under burning a candle per instance).

Special tip about our  Leaf Art candles...
Our candles were designed with the idea of retaining the outer walls of the candle to create a "lantern" look.  As the flame gets lower and lower in the candle the glowing appearance gets more dramatic.  You can achieve retaining the wax outer walls by burning the candle close to, but not all the way to edges.  Once the wax has melted/ liquefied to about 1/4 inch- 1/2 inch from the edge, blow out the candle.  If you opt for complete candle consumption the metallic flecks are absolutely non-flammable and will roll up as the wax heats around them. 

#3 Keep your wick trimmed to 1/4 inch in length...
This will control the size of the flame and therefore the amount of heat generated, plus prevent a flame from smoking.
...and keep the area around the wick clear of debris.  Things like wick cuttings or matches not only look unattractive, they are potentially flammable.

#4 Keep your candle's flame centered.
This will promote even consumption of wax around the wick and therefore and evenly burning candle.

#5 Keep a burning candle AWAY from drafts. 
Drafts can be a result of everything from the obvious, like open windows, doors, ceiling fans etc., to heat sources like fire places.  Beware of burning a candle on the mantle of a fireplace when the fireplace is in operation.

#6 Always place your candle on an appropriate base.
This will help safeguard surfaces from spills and stains ( candle's pigment can penetrate porous surfaces like wood).

#7 When blowing out your candle, be careful of the force you use. 
Ideally, a proper candle snuffer would safely extinguish the flame but many of us rely on just blowing out the candle.  Please do so with caution as hot liquid wax can spray very easily.