I personally will continue to burn the candle and meditate on the outcome of my spell until the candle is burned down. I never had any problems with tossing the remaining wax. I would say it depends on the spell. If it is important that it is taken care of properly you might concider burying it.
I bury any remnants of a spell which is finished. However, if it is a spell with work still to be done, I keep the candle and the other parts and repeat them until the candle is burnt away completely. A good way to do this is if you are using say 2 crystals and a poppet. Place all three in a jar and a lid, and place the candle on top. When the candle is burnt away you can then bury the whole jar someplace it will not be disturbed, or you can get another candle, consecrate it to that spell and keep your magical working going.
I feel it depends on what type of spell you are doing, and what kind of energy you don't mind keeping around. For most spells I bury the remains or toss into a camp fire. However there are a few I will save wax from and melt down to make new candles. For example, my healing and prayer candles get recycled. I put a lot of love, kindness and caring into these, and find the energy left to be very uplifting. It is all in your own personal preference. I would not suggest cursing someone and keeping the remnants around your house >.>