Creating an altar is something that varies a lot by tradition, but this is a guide on how i personally made and maintain mine. Hopefully this is helpful to someone!
Step One- Planning and Sourcing
In my tradition, there isn't necessarily a huge difference in making personal vs deity altars. As I've heard several of my teachers say- an altar is the place in your home where magic is always welcome. if you wish to add to that by including deities that are always welcome or honored in that space, great! if a deity does request their own specific altar, no problem!
The more complicated aspect for me, is that i feel deeply i must be in right relationship with the items on my altar. Part of this is everything being ethically sourced. All things on this table were either found by me, purchased from a small local business I trust, or received as a gift. These items have been accumulated over the last 5 years of my practice. If you are just starting out and feel as i do about sourcing, you might have a lot of arts and crafts projects ahead.
What aspects of your practice you feel are necessary to represent on your altar? Should you have artwork? Plants? Symbols or sigils?
What work will be done at your altar and which tools should be there? Are you doing meditation that requires a nice smelling herb or oil? Will you be doing spells on it that require big empty space?
Step Two- Find or Make Materials
My recommendation if you don't have the budget to buy a specific dedicated table/ shelf for your altar is to clear a space where you feel the most presence of magic in your life. My earliest altars were cleared off spots on bookshelves and in the kitchen.
Now that you have a list of themes or specific items you want on your altar, go on a nature walk and find things that call to you. Whenever I go to new or interesting places, I keep my eyes peeled for things that might be useful in my practice. Don't take too much, and ask permission from the land before leaving with anything. If the item feels oddly heavy as you walk away with it- give it back.
The main thing i do at my altar is meditate and pray to deities. Because i view this space as my gods' front door, i care a lot about it looking aesthetically pleasing. I am not part of a tradition where it matters what things go on the left or right, the elements are not associated with cardinal directions, and deities aren't really unsatisfied sharing an altar with each other (even if they may not get along in some lore). Because of this, i just lay things out intuitively, aiming for some symmetry. I also prefer to do spells outdoors, so my altar doesn't need to have a workable space beyond a nice spot to charge things.
Do I feel the need for my altar to have directional correspondences?
Is it important to me to optimize aesthetics?
I work a lot with the seasons, and this is meant to have some nice summertime vibes. With the harvest season coming up, i'll definitely redecorate it.
If anyone has questions please let me know
go n-éirí leat! good luck!