This was written for a public class and is designed for any one that follows a Magickal path. It is not necessarily Wiccan based. I drew my information from many sources.

Types of candles

There are many types of candles out there to use. There are tapers, votive, tea light, jar candles or Novena, also known as 3, 7, 9 and 14-day Jar candles, Jumbo, The 7 knobs, crucifix candles, male and female figure candles. The list is really endless, so I am going to focus on the main candles that are primarily used in magical workings.
You can use any candle for working candle magic; it does not have to be any particular size, shape, or even color! The only reason for these are to help the performer keep more focused on the work to be done.

Candle Types

Tapers are traditionally used on altars, but are also useful for a spell where you want quick results. Birthday candles also work well for this.

Votives can also be used for quick results. You can also put these into jars, and use them as mini jar candles.

Tea light candles can be used, but they only burn for about an hour, and are enclosed in a metal container. I do not recommend them, since they are not practical in magickal purposes.

Jar or Novena is one of the most useful candles to use in magick. You can get these in a wide arrange of colors, with and without images, painted and unpainted. The custom originated in ancient Egypt and has been widespread since then. The idea is to burn away all the old troubles or mistakes and start anew, with a clean unobstructed viewpoint. The Novena candle is best to start at the New Moon.
According to many once you light a Novena candle it should never be extinguished. That is, it needs to burn until it goes out on its own. Many recommend that you place it in a metal pie or cake pan and place it where it will be safe to burn for the duration of the candles life. This is in case that the glass breaks, all the wax will go into the pan, and be less likely to catch fire.

Jumbo candles come in wide range of colors and sizes; the broader the diameter the longer it will burn. A useful way to use this candle is to mark it into sections for each day that you want to use it. You simple burn it to that marking daily.

The 7-knobbed candle is a popular candle among many practicing magick. The idea is to burn one knob each day to bring about the desired results. You can also get a 7-color novena candle, to have the same effect.

Reversing candles are used when you want to reverse a spell or hex that has been cast upon you.
Separation candles are jumbo red candles which have been hand-dipped in black, covering the entire candle. The red symbolizes the person that you wish to be freed or liberated from bondage or enchantment of an undesirable person.

Image candles
Male/Female are widely used for love magick, but they are most useful in healing magick. Depending on what type of magick you practice, you can also use them for hexing and banishing.
Black cat candles are traditionally used to banish bad luck.
Skull candles are commonly used in rituals for the healing of terminal illness to banish away death. They are used with an astral candle in the appropriate color. The astral candle needs to burn for the same amount of time as the skull candle.
Satan candles or devil-be-gone are traditionally used as a banishing of evil.

The Triple Action candle is believed to release the highest magickal vibrations. It is also used in healing, banishing, and hexing.

Memorial candles burn between 24 to 30 hours, and have multiple purposes.

Color Symbolism

Primarily when you chose the color of candle to use in magick, you need to decide what the colors mean to you, not anyone else. I say this because color symbolism is very personal. What you attribute to a color is what will be used when you are using a candle for magickal purposes.
I will include a basic color symbolism guide, but still use what feels right for you!
You also need to know what are the best days to do certain types of workings; all of this is needed to do certain types of workings. But the same goes as with colors. You have to use what is best for you, not anyone else. Knowing astral colors will help as well.

Days of the week are also useful to know. There are supposedly days that magick and colors are more powerful. If you believe in this, then it will work. But if you do not, it will not make any difference.
Herbs in candle magick are also very important to know. Herbs have such a natural power, and they can transform a simple spell into a very powerful one. I do recommend that you further your reading on this subject.

Working Candle Magick

Now to start a working, I recommend that first you cleanse the candle; this is to insure that it is in its purest form. To do this, you would cleanse it as you would any tool that you would use in ritual or magick. A simple one will do, such as the following:

Have on your altar:
Candle, incense, bowl of water and bowl of salt.

First I would light a candle and incense.
Then I would say: I cleanse this candle by Fire and air.
Pass the candle though the candle burning and then the incense.
Next say: I cleanse this candle by Water and Earth
Pass through the bowl of water and salt.

Dressing Candles

Dressing the candle with oil is as important as any other step. Use whatever oil you prefer or what a specific spell asks you to use. What is important is the direction you dress the candle. To bring something to you, rub oil on the candle in a downward motion from the top to the middle and then from the bottom to the middle. To send something away from you...you rub the oil from the middle of the candle out to the ends. Never make a back and forth motion as this defeats the purpose. Then say the following:

I cleanse and consecrate this candle in the name of the Lord and the Lady. May it burn with strength in the service of the light. Then state your intent or the purpose of the candle.

You can at this point use herbs and roll or pat them on; the oil will work as a fixative.
You can also hollow out the bottom of the candle using a hot knife; you then pack this with herbs and oils, then use the candle wax that you had dug out to seal it back up.

Inscribing

If you inscribe a candle you should use your Athame. The same principle as dressing the candle is used: To draw something to you, write from the top to the middle, and then from the bottom to the middle. To repel things, write from the middle to the ends.

Also you can use string. I recommend embroidery floss for this. You can get any color that you may associate with the spell that you are working. You first anoint it with oil and herbs if you like, then you take the floss and wrap the candle spiral upwards to bring something to you. Spiral downwards to send something away.

Recommended Reading

There are many useful books; this is just a few.
The Magic Candle, Charmaine Dey, Original Publications, Bronx, NY 1982
Practical Candleburning Rituals, Raymond Buckland, Llewellyn Publications, 1998
Advanced Candle Magick, Raymond Buckland, Llewellyn Publications,
The Complete Book of Incense, Oils, and Brews, Scott Cunningham, Llewellyn Publications, 2000
Cunninghams Encyclopedia of Magical Herbs, Scott Cunningham, Llewellyn Publications, 2000
The Master book of Candle burning, Henri Gamache, Original Publications, Bronx, NY
Rituals and Spells of Santeria, M. Gonzalez-Wippler, Original Publications, Bronx, NY
Voodoo and Hoodoo, Jim Haskins, Original Publications, Bronx, NY
Candle Burning Magic, Anna Riva, International Imports, Los Angeles, CA 1998