I believe the altar is the very center of the magicians core working space, and that the same space should be used each time magick is performed (if possible) as the residual energy from your workings will collect into your altar, making each working even more potent with the energy remaining from the last working. If using any space available, this residual energy can start collecting everywhere which is fine if you live alone but if you live with others they may begin to feel that energy all over the house and if they have not been trained to also work with dark energy, it can make non-magicians irritable, negative, or even scared out of their mind.
Here’s a good idea, I did this when I was a young adult just out of high school but still living with my mom trying to start my adult life. I bought a large wood chest that opened like a treasure chest, flat on top, looked like a regular storage chest at the foot of my bed. You can find chests that have a pull out tray that sits just inside the chest towards the top but allows for space underneath. Put your magickal tools in the bottom of the chest below the pull out tray and fill the tray with items that look normal, like a blanket or trinkets. If you can’t find a chest with a tray you can buy a flat wood panel that will fit inside and cover your tools with the panel, then lay the normal items on top or even place a few board game boxes on top to cover the tools.
A normal onlooker, if nosey, will only notice the junk inside of the chest on top and will usually not look further, thinking it’s a chest of random junk. You can also cast a protection spell on your chest so if anyone does peek inside, the urge to peer further will leave their mind and they will walk away. When you are alone, pull your tools out of the chest and close the lid. You can place an altar cloth on top of the lid and use the lid as the altar itself. Once done, just put everything back inside and close the lid. All your tools and magickal energy will be contained within the chest so any normal items you place inside to hide your tools, make sure it’s items you don’t use often, that won’t need to be removed as those items will also become tainted with that energy which will be released if you remove the items and later place them around the house, or you could also create a bubble of protection around the normal items to shield them from absorbing the energy, so they can still be removed and used in your home if needed.
As Eric mentions in WOD, I found that the more simple my altar is the more effective my magick is. My first altar, several years back, was loaded with symbols, fancy altar cloths, daggers with decorative handles, and posters hanging above which can cause confliting results if you are working with one demon and your altar has symbols of 5 different demons posted all over.
The only real tools you need:
-Ritual dagger with 6" blade, plain straight blade sharp on both edges
-Chalice, not too decorative if possible, either black or silver
-A charcoal incense burner
-Charcoal pellets made specially for use indoors with incense burners only and granular or resin based incense
-Altar cloth, plain black is best or solid colors to represent the color of the entity you are working with
-Black mirror for scrying and a black cloth to wrap it in when not in use
All the other tools are just fancy non-required extras.