I had a teen ask me today, "How do I know which God and Goddess to worship?" She was interested in Wicca and during the course of our discussions, she made a statement that seemed to imply that she thought that there is one God and one Goddess in Wicca. I let her know that "Lord" and "Lady" are titles, not individual Deities. She was non-plussed to learn this because she had read several books on Wicca and she was under the impression that all Wiccans worship the same Lord and the same Lady. Not so.
I realized that this can be very confusing for new seekers and those who are trying to learn Wicca without benefit of instruction from an initiate. Too, depending on which Tradition we're talking about, different initiates will give different answers to the same question. Here's the skinny from my viewpoint.
Some Wiccan Traditions and covens work with certain Deities and if you're a member of that group, your group circles will consist of working with those Deities and no others. Other groups teach that the Lord and Lady have many faces and work with various Pantheons of Divine Beings in turn and/or with several Deities in turn. Solitary practitioners may work with whole Pantheons, several Pantheons, or with individual Divine Beings exclusively. And some do simply work with the face of the Horned One (also a title) and the face of the Great Goddess (a title) that suits them. Any and all of those approaches work within the framework of Wicca.
Wicca is simply an organized framework by which to approach the Divine as understood by Neo-Pagan people. Wicca is orthopraxic, which means that it is defined by practice, not by belief. So if you observe the Sabbats and Erect the Temple as it is done in Wicca, Whom you invite into your circle is an individual decision.
But how does one know Whom to invite? Therein lies the question. I had the luxury of being "raised" in a Tradition that works with various Pantheons for extended periods of time. In my first year, it was the Greek Pantheon. My second, it was Welsh. Then there was the Norse cycle we did some time after I was initiated that introduced me to my beloved Freya. I got to work with these Gods as groups and individually, and be exposed to their stories, the flavor of their cultures, and see them invoked into my High Priest and High Priestess so I could speak with Them directly. If you don't have that luxury, it's harder. Here are my suggestions:
1. I strongly encourage interested people, whether they have a Matron/Patron or not, to consider working with various Pantheons for whole solar cycles. The exposure to the complete stories of a Pantheon and the opportunity to work with various Deities from that Pantheon in seasonally appropriate ways gives rise to a complete experience of the Wheel of the Year through the lens of that culture's myths. This is valuable beyond measure and can only be appreciated if undertaken. I've never seen anyone who did this report that it was a waste of time.
2. If one feels strongly about being called by a Matron or Patron God/dess, it is in my opinion respectful to study that Deity's culture and the complete available myth body of the Pantheon from which that God/dess hails. Cultural appropriation without due diligence is in my opinion disrespectful to the Divine. And one cannot truly understand one's Matron or Patron in a vacuum. You can't completely grock Isis if you know nothing of the rest of Her Pantheon, nor can you understand *why* certain things are sacred to Her.
3. Some of us do have multiple Matrons and Patrons and yes, They sometimes come from different Pantheons. Some others of us insist that working with only one Pantheon is for them and that they only want one Matron and Patron. So be it. But again, as I work with Aphrodite, Bloddeudd, Brighid, and Freya as well, I study *all* of their respective Pantheons' stories to the degree that I can manage to do so and I try to spend a fair amount of time in devotion to each.
4. It is bad form in my opinion to approach a Divine Being only when you want something. You wouldn't like it if I only called you when I needed a ride or a hand-out, so don't do it to a God or Goddess!
5. It is perfectly cool to work with larger, more generalized Deities such as Sky Father and Earth Mother in Their various forms. Don't let anyone tell you that you can't. My tendency when working with, say, Earth Mother, is to use many of Her names and study how the various cultures who worship(ed) Her viewed Her, propitiated Her, and remembered Her. So rather than going the "micro" route of worshiping Gaia (Greek Earth Mother), I would do the "macro" approach of worshiping Her as Gaia, Pachamama, Phra Mae Thorani, Terra, and Her many other names.
So how do we know when we are "called" by a Matron or Patron? That's completely subjective. Some of us are called in dreams. Some of us have recurring things happen that keep pointing to a particular Deity or Pantheon. A devotee of Bast I know kept having cats give birth in her barn over and over and had a picture of Bast actually blow onto her windshield during a storm. Or perhaps you will read about a God or a Goddess and suddenly be filled with tingly warmth and love. It's like any other type of love, I guess. You just know.