Witchcraft by definition is a set of skills.(1) What skills then does the Witch practice? This topic began with a question of book recommendations. Here are my views.
I would hope those reading won't get turned off by the fact that I will be quoting - dare I say it? - the Bible. Understand that the purpose in doing so is placing in context how long such beliefs have been seen as witchcraft. Deuteronomy is believed to have been written around the 7th century BCE and so I will quote what are still today believed to be practices of a Witch:
"There shall not be found among you anyone who burns his son or his daughter as an offering**, anyone who practices divination or tells fortunes or interprets omens, or a sorcerer or a charmer or a medium or a necromancer or one who inquires of the dead, for whoever does these things is an abomination to the Lord." (Deut 18:10-12)
These are still skills of the witch though "charmer" here can also mean "those who work with herbs" as women who utilized them to "charm men" were frowned upon. In Exodus 22:18 "Thou shall not suffer a witch to live" in the original hebrew is "M'khashephah lo tichayyah." M'khashephah is seen as a general statement regarded as "sorcerer or charmer," but kashaph (keshaph) could originate with kash (herb) hapalah (user) which would simply refer to those who use herbs for other than medicinal purposes. In the Greek this was translated as pharmakia that would have been what the original "poisoner" was that King James changed to "witch" later.
Then there is the "one who inquires of the dead" though I have seen this all translated as "communes with spirits." The Greeks referred to such practices as theurgy. While there is a lot more to this concept the basic idea behind it is an outside force helping the practitioner. That could be a spirit or even a deity. The practitioner is asking for assistance to accomplish their needs.
Sorcerer also refers to one who works with "magic." While witches are particularly associated with low magic (theurgy) there are Mages and Witches who work with what we refer to as the higher magics. Ceremonial magic is the first philosophy to come to mind. The Greeks used the term thaumaturgy meaning working "miracles" or "magical feats." These magical feats don't necessarily include the use of an outside spirit or deity to accomplish their goals.
As we can see the simple break down of even thousands of years ago as can be related to today witchcraft is the skill set of a witch including herbalism, divination, low magic, etc. There is no "religion" involved. It is simply that - the practice of a specific set of skills. Because the practice includes a decent number of individual skills it cant be covered in one book. In fact, most of the witchcraft books I have looked through really focus more on the history and then throw in a few random spells to make the reader feel more powerful as a "witch." Anyone using these types of books to deem themselves a witch needs to do a lot more digging spiritually, scientifically and historically.
We see in many cultures the inclination towards divination. In Greece, Oracles were consulted; in Celtic cultures, the Ovates were the diviners; we have palm reading with the Gypsies and Runes with the Norse. These are by no means the only forms of divining. One modern divining technique that comes to mind is taking a piece of wedding cake home and sleeping with it under your pillow to reveal the (wo)man you will one day marry. These abilities were said to be a gift from the Gods, but their cultural use has seemed to dwindle down to that of childrens games or something fun to do on occasion in the mainstream.
The gifts of herb knowledge were passed down from generation to generation across the globe. From tea concoctions to tree bark almost every region had their specific vegetation that was used in healing. Those who were proficient in these herbal remedies, outside of general knowledge, were the witch doctors and later the apothecaries. We have slowly taken this knowledge of the land and made our synthetic world. Do I necessarily disagree with this practice? No, there is only so much to go around in nature, but it seems with these synthetic drugs we have lost touch with their origins and now dismiss herbal remedies as new aged "hoopla."
Ritual is a practice we seem to have lost touch with in a more secular world. Obviously, a ritual is significant to religion. When one goes to church on Sunday they are experiencing some sort of religious rite. When I speak of ritual, however, I am talking beyond fancy words, pretty knives and smelling up a room with incense. Life in itself is a ritual of sorts. When one takes the time to bake a cake for the family they are taking part in a ritual. Slowly breaking and beating the eggs, mixing the flour, heating the oven, preparing the pan. All of these actions are a set of steps in a accomplishing a task set forward. In the end, there will be this (if you are skilled) glorious, moist, and satisfying cake for all to consume. Even simply using the bathroom (while not the greatest example, but definitely a universal one) carries a ritual of sorts. It is the ability to appreciate not only the finished product, but the steps it took to accomplish the task that makes it ritualistic. It is when you take pride in every little step that it truly becomes almost sacred(3) and, in essence, supernatural.
I will tackle the topic of magic since, I believe, it is a staple of witchcraft. Magic is simply the use of those energies that surround us and connect us to everything, yet we can not see or touch it. Again, magic falls under the supernatural definition because, in a sense, it is beyond the realm of truly understanding, though though cultures like the Greeks and those before and after have tried. Magic, in it's simplest form, by this Witch's experience, is more of a feeling, like the air that we breathe in. We know for a fact air exists because we breathe it in daily, but we can not see it, we can only see what it affects. When you light a candle, you watch as the air causes the flame to flicker in different directions. Pick up a dandelion and blow all of the seed pods away, watch as the air picks them up into the open space. Magic is the same. It is that feeling that we know everything will be alright, or that feeling of being drained when you have done nothing laborious. Magic is not just the existence of that energy around us, but the use of that energy outside of a realm of simple prayer. When we use magic, we are not asking permission from an outside force. We are saying, this energy is mine to respect and control and I will put it to use wisely. Our only proof is in getting that promotion, healing our friend or finally having that person you like kiss you.
I won't talk a whole lot about spell craft as it really is simply a specific ritual in combination with all I have already mentioned. Spell craft is the act of using magic in a ritual sense, perhaps in combination with herb knowledge and divination to gain a specific outcome. Spell craft is a specifically sacred ritual that requires the acknowledgement of every step because one wrong move and you have blown your whole purpose. In many cultures, there was, yet again, one person or two people in the tribe that were responsible for the exploration of this practice. The most commonly known were the medicine men of the Native Americans, the Druids of the Celts and the Brahmins of the Hindus.
Witchcraft is all of these skills and more. It is the embracing and use of these supernatural abilities. No one book can truly explain the use of these skills to anyone. Many books can give a general view of them, but if you truly want to learn the skills of the Witch go out and make a set of runes or tarot cards. Find information on not just magical herb significance, but practical as well. Take the time to notice the steps it takes to walk to the car, to make breakfast, and to change from winter to spring. When it comes to spell work go with your heart. Sure a book can tell you what color the author would use for what purpose or even what incense, but in the end, if it feels right to you than that will make your focus ten times stronger. As for magic, that is a tough one. I do say go out and find information on physics and the Law of thermodynamics to better understand how magic works. Without that simple knowledge, you are pretty much working in vain, however, those books will not tell you how to feel all that is around you and to acknowledge the connection you have to all things. Only you can take the time to fully appreciate, understand, and utilize the energies that surround us.
Books can certainly give you the basics in regards to these skills, but in the end, what makes one a Witch is putting those skills to use given the knowledge from those books.To truly be a Witch one must practice, practice, practice.
1) Craft: skill in planning, making, or executing
2) Supernatural: of or relating to an order of existence beyond the visible observable universe
3) Magic: the use of means (as charms or spells) believed to have supernatural power over natural forces
**Side note - Just to touch on the "burns his son or daughter" I think this was a misunderstanding in and of itself about what was possibly going on. Perhaps a dedication to the Gods or even a reference to some sort of human sacrifice. This is obviously not something that is common place in one's house or backyard, but would have been a tribal experience and if thought about is still regulated by the heads of state to this day. While I personally wouldn't equate this specifically to witchcraft, a sacrifice (living or other) is still done in many communities.