As a part of my daily practice, I do a set of prayers in the morning, generally to the Almighty but occasionally to other powers, as the weekdays and occasions demand.  However, part of my morning prayers include a quick general offering to any and all spirits willing to partake in it.  I offer a small glass of water (mixed with rose water and Florida water when I’m feeling fancy) and a stick of incense (Song of India’s temple incense, generally, since I get it in bulk), which is generally sufficient as a general offering.  I generally make this offering as the first offering I do after my prayers to the Almighty, so that any other spirit I call upon afterwards can also partake of the offering as they come into the area of the altar.

I announce and dedicate the offering with the following prayer, which developed into a more-or-less stable form after repeatedly making stuff up on the spot every morning.  Maybe you might find it useful in your own practice, or something like it.

Come, all you spirits who hear and see me!
Come, all you spirits coming to this place, leaving from this place, passing through this place, or residing in this place!
Come, all you spirits, whoever you are, whatever you are!
Come now to this altar and partake of this offering!

Whatever name you take, whatever form you take,
Be you god or goddess, angel, demon, or messenger,
Be you ghost, ghoul, spirit, soul, or ancestor,
Be you of the north, south, east, west, sky, or earth,
Be you fae, sylph, salamander, gnome, or undine,
Be you light or be you dark,
Be you of any element, any planet, any force, or any realm,
Come now to this altar, and partake of this offering!

I give you now this water and this incense,
I give you this freely and joyfully, and ask that you accept them in the same.
I give you these offerings as a symbol of my love, goodwill, honor, respect, and joy.
Accept now this water, sweet, clean, and fresh, that it may refresh you, cleanse you, and cheer you.
Accept now this incense, sacred, whole, and pure, that it may satisfy you, strengthen you, and fortify you.
Let this water manifest to you how it should best manifest for you, whether as rivers of nectar or lakes of blood, that it may best be suited for you.
Let this incense manifest to you how it should best manifest for you, whether as forests of flowers or mountains of flesh, that it may best be suited for you.

Come and take your fill, o spirits, of these offerings!
Come and take your fill of this water and this incense, and go on your way!
Let this offering aid you in your tasks and lives,
Let this offering sate and please you!
As you take your fill of these offerings, keep in mind who it is who gives them to you, and remember me.
Let this offering of goodwill be taken in goodwill, of peace in peace, of joy in joy, of love in love.
Take your fill of this offering, and go on your way, and go with my peace and blessing.