This is an easy to follow tutorial: http://livethefancylife.com/diy-making-new-candles-out-of-leftover-wax-and-old-candle-jars/
Make sure at least half is paraffin wax. Colorize with old crayons in complimentary colors. Place the wax and crayons in a metal coffee can. Place coffee can right side up in a pot with an inch or two of water so it acts as a double boiler. Place on stove and turn on stove low to medium heat. Can stir with a disposible wooden or bamboo chopstick.
Use an old ceramic coffee mug for a mold. Tie a piece of wick around a pencil at one end and leave enough length to lay pencil across top of mug and wick should just touch the bottom of the cup. The pencil should be positioned so the wick drapes down into the center of the mug. Trim off any excess wick. You may want to set your mugs on an old cookie sheet, wax paper or foil. Newspaper is not good because any spilled wax will bleed thru to your table and stain it permanently. When wax is melted in the coffee can, turn off stove, and carefully lift can out of pot with oven mitts on your hands. Carefully pour wax into mug so it fills the mug and doesn't quite reach the pencil. Let cool and set overnight. If you put mugs in the refrigerator, the wax will create a cupping vortex in the middle, and you will need to pour more wax in to fill the void. This may or may not be a desired effect. After you get the hang of this, you may want to try making striped candles, by pouring an inch of wax into the mug, and after that sets, pour another color, let set, and so on. You may also want to try putting shreds or bits of contrasting color crayons in the wax after it is poured, try florescent crayons, sparkle crayons, or tilting the cup slightly while it sets. If you do this, I recommend you sit the mug in a pan filled with sand to keep it from tipping. Sand candles can be made by pouring the wax into holes dug in the wet sand. Wicks can be retro fitted by heating up a metal skewer on the stove and piercing a hole thru the wax to thread it thru. Be sure to protect your hands with oven mitts and wear an apron or smock as wax will ruin your clothes. Stand well back when pouring, as hot wax can splash and burn your skin. Wear eye protection.
There is a candle maker kit that can be purchased at hobby stores or online that melts the wax then it can be drained into a mold. I have had one for many years and have melted old candles down to create new ones, plus it's very easy to use! I hope this helps!
I use an old crock pot. I ,let my old wax, add in some crayons for color, and sometimes some oils for smell. I use cotton threads for dipping. Temperature remains constant.