Let me say this: An altar can be anything, anywhere - permanent, temporary, and made up of anything. It can be your coffee station, a shelf in the bathroom, or a collection of things you bring out when you write. Hell, it can be the contents of your everyday bag of choice.
I've included a picture of one of my altar tending sessions just to show how it can be anything, about anything.
When revisiting your altar or approaching it's creation for the first time - this is what I recommend.
Ask these questions, or questions like these:
Where have I been consistently feeling most tender in my physical and emotional bodies?
In what places do I feel stickiness or blockages?
In what ways has my inner child/inner teen been asking for attention?
Look for items that address, remind, and encourage integration and vitality around the answers to your questions or the questions themselves (especially if the answers feel hard to come by, which is entirely normal!) These are my personal favorites...
Artwork - your own or someone else's
A card, like a Tarot card or animal card
Notes to self
Artifacts from life
(like my great aunt's jewelry, given to me by my aunt after I lost all of my heirloom objects in a forest fire in 2013.)
And other things.
The essential thing here is to be intentional. Perhaps write down what each object means to you -- internalize this.
Your altar is there to partner in your life, in your personal revolution. Without you, without your attention and action - an altar is simply objects arranged.
When I speak of generative energy, this is what I mean.
The energy you put into your altar is the energy you are putting into your essential being. Every time you revisit the memory of creation, you fortify the intentions you set and energize The Self. The energy might become more powerful through the discipline of thought (a boundary created between your gut and mind), action over time, a significant and immediate mental shift (the aha moment), or decisive new actions.
No matter your intention, mean it with your whole being - be consistent and patient. Witness your development over time by chronicling your thoughts, ideas, and behaviors in a HEALTHFUL way.
Tend away from these things while revitalizing your altar.
Force, pressure onto others or situations outside of your control
Grasping, reach for your best self
Begging and bargaining, don't beg anyone to change, stay or make trades to get what you want
Holding onto things that are actively trying to get out of your way.