Altars in Witchcraft
I was just going to include this in my original page on pagan altars, but decided I'd just make it separate.
In a lot of ways, witchcraft altars are similar to pagan altars. Depending on practice, these elements may change, but typically they include stuff like an altar cloth, candles, maybe statues of deities if the person includes them in their practice, incense burners, et cetera. If they're Wiccan, there's likely items representing the elements, a chalice and an athame. Witchcraft altars, in my experience, tend to have more variance because some people tend to keep them very practical (ie little to no decoration, only includes items directly used in spellwork/etc) while others tend to make them very aesthetically pleasing (to varying levels of practicality).
I would say that, for witchcraft, you also need an altar. It does not need to be permanent or have anything that is designated as "witchcraft only", it is just important to have a space that you chose to serve as an altar, at least in the moment. Intention is also important here. I elaborate on this more in my page on pagan altars.
Setting Up An Altar
Again, this is with more "traditional" permanent altars in mind. The steps involved here are essentially the same. You'll want to determine the location and make sure you wipe it down and do any cleansing, if that is part of your practice.
What Do You Put On an Altar?
This is where we start to diverge from the pagan altar page. Witchcraft encompasses a lot of different things, so what is going to be included on an altar really depends on what your specific practice is. There are some common items, though not all of them are relevant to everybody.
Altar Cloths
Included for the exact same reasons as they are on pagan altars: they're both decorative and practical. Altar cloths can make an altar feel more "unified" and also protect the furniture from wax and incense ash...and whatever else you may accidentally spill or drop on your altar.
Bowls, Plates, & Cups
Some witchcraft involves the use of cups and plates, but some witches also use them for offerings, if they include any spirits or deities in their practice. What types of bowls/etc you need will depend on what you're using them for. If it is for offerings, I discuss them for that purpose more in depth on my pagan altars page...sorry to reference back to that so much!
Candles
Witches and pagans loooove candles. I discuss the role of candles when it comes to a pagan practice (which no doubt has overlap), so this will be purely about candles in the context of (deity agnostic) witchcraft.
Candles are very popular in witchcraft of all types because they come in so many shapes, colors and scents. Chime candles are probably the most common shape of candle found in spellwork because they burn relatively quickly, come in many different colors and are inexpensive (...unless you're getting them from some specialty Etsy store or something). It's easy to align candles to your intentions and needs.
I personally associate burn time with how "potent" the spell will be and I'm honestly not sure if that's something I just came up with or if I actually picked it up somewhere. I use larger candles for more serious spellwork though.
Often, witches will keep a variety of candles that they know they're likely to use (ie my partner and I keep tealights and chime candles) for the sake of convenience. Some people (me included) also like to have candles that serve to set the mood, ie lighting a candle before divination (perhaps one that can aid in focus).
Incense
Incense can also be used in spellwork or in setting the mood. A lot of witches will burn incense while working on other spells, to help with keeping their mind on their intended outcome. It also just smells nice.
Grimoire and/or Book of Shadows
While this isn't always an item that is kept on an altar, it is usually nearby. A grimoire serves as a reference book so, it makes sense that it would be somewhere convenient.
A Book of Shadows is a Wiccan thing and is essentially a witchcraft journal where the practitioner keeps their notes and insights.
Spell Ingredients
Another category of item that may or may not actually be displayed on an altar. "Ingredients" encompasses a near infinite number of things so, it's a little hard to be more specific. Often times, however, this includes jars of herbs and vials of essential oils. I wouldn't recommend buying anything you aren't sure you're going to use relatively soon.
Tools
Another vague one, but depending on what sort of practice you have, this may include: tarot/oracle decks, rune stones, crystal balls, athames or other ritual daggers, chalices, mortar and pestle, candle snuffer, something to carve candles, wand, lighter/matches, et cetera.
Other Items
A lot of witches also include purely decorative items on their altars. I would definitely encourage this (particularly if it helps you feel more connected to your practice), but it is easy to fall into the trap of making your altar look pretty, but also entirely impractical. It is more important that you are able to actually use your altar. Social media convinces a lot of people that their altars must be extravagant and beautiful, but a lot of those altars are also not being used by the people posting them. How could they be? The amount of stuff on them is a fire hazard, they'd knock everything over trying to get to their herbs and any amount of wax drippage or stray incense ash would ruin their decorations. There needs to be a balance between practicality and aesthetic appeal.
Further Advice
My advice is always to avoid falling into the consumerist trap that a lot of witchcraft and pagan influences tend to promote. You do not need anything fancy or even specfically dedicated to witchcraft. You can use cups from the kitchen (as long as whatever you're putting in them is safe) and herbs from the grocery store. Witchcraft is a spiritual practice, not a hobby you need to sink hundreds or thousands of dollars into to be able to be "good" at it.