Calling the Quarters. It's a staple in many rituals. But, what exactly is it? What does it mean? And, why do we do it? There are no "one-size-fits-all" answers, but I can tell you briefly how it works for me.
I view the Quarters as "guardians", but not necessarily as physical guardians of the directions; more as the "gatekeepers" to the qualities or characteristic represented by each element. Some Traditions call them Watchtowers, but that has never really resonated with me. When I call the Quarters, I am invoking the qualities associated with each element, in an effort to make myself more aware of, and better able to focus on those characteristics to aid me in my work.
The East is associated with intellectual persuits, clear thinking and communication. By recognizing the Guardians of the East, I am focusing my attention on these qualities and opening myself to receiving inspiration and guidance along those lines throughout my ritual working. The same holds true for South (passion, determination), West (emotions, love, memories, mental health) and North (stability, grounding, physical health). Which element you associate with the directions may vary by Tradition, and therefore the qualities associated with the directions may change. This is fine. Really, it is all symbolic and merely acts as a reference for us, rather than representing any actual, physical relationship.
There is contention on how best to release the Guardians when a ritual is completed and the Circle is being opened. It is popular to end with a line similar to "stay if you will, go if you must". Some sources contend that you should send the Quarters on their way with no invitation to stay, stating that it is just asking for trouble. While it is true that the Guardians are not human, and cannot be expected to act/react the same as we do, it does not necessarily follow that they will wreak havoc by being allowed to stick around. Personally, I have found that rather than banishing them (which seems a bit rude), if I give them the freedom to choose whether to remain present or not they do not cause any problems. They are not infantile, as has been suggested; rather they are a different sort of being that recognizes friendship and respect and responds in kind.
And on that note, here are sample Quarter Calls for casting and opening the Circle:
"Spirits of _________, Guardians of the _________, I(We) invite you here to this Circle to witness what I(We) do and lend what aid you may. Hail and Welcome."
"Spirits of _________, Guardians of the _________, I(We) thank you for your presence and assistance in my(our) work this night. Stay if you will, go if you must. Hail and Farewell."