One of the first things talked about or learned by newcomers to the Craft is the use of Quarters. Essentially, Quarters refer to the magical circle divided into four equal parts. This is typically done by combining two diagrams of a quartered circle.
The first is:

This is the image in mind when people think of a Circle divided up according to the compass points. North is at the top and it continues clockwise through east, south, and west.
The second diagram shows how the circle is quartered for these divisions magically:

*If you imagine both of these overlaid on one another, you have the spokes of the Great Wheel of the Year — but that’s another topic for another time.
Quarters are a combination of cardinal directions/compass points and the elemental powers, beings, and energies aligned with each of those directions.
In a Quarter Call, the Witch typically stands facing the Quarter they are addressing and asks that the beings associated with that Quarter attend the rite, lend power and energy, or offer protection and guidance.
Elemental associations may vary from tradition to tradition, or from Witch to Witch, but the most common pairings are:
North = Earth
East = Air
South = Fire
West = Water
The beings or energies invited to attend may be the elemental energy of that respective direction, the Elemental Guardian or Lord (these are often considered to be the Lords of the Watchtowers), Angels, Fae, or other spiritual beings, Power Animals, or various other entities with the appropriate associations.
Some Witches work with mystical animals and may call dragons, gryphons, or unicorns.
It is also not uncommon to invite the Ancestors and/or Mighty Dead to attend as Quarters for certain rites.
What is most important is that if you call quarter energies to your rite, you are balanced and specific. Your invitation speech needs to include what purpose the individual entity is being summoned, stirred, or called to do.*
Personally, I avoid calling gods and goddesses for Quarters. Some Witches do this, but I do not. It’s a matter of personal choice, but in my experience and my opinion, it’s rude. Deity belongs in the center, the main stage if you will. Usually, the Witches who will invite a deity into a quarter are those who see deities as facets or parts of one mega-God or mega-Goddess. There’s nothing wrong with that belief — it’s a very common one, in fact — and doing so if that’s your experience and how they present themselves to you, feels natural.
But for me, I just can’t do it.
Balanced and Specific
Balanced – Use the same energy types in each quarter to keep your circle balanced as a whole. I suggest if you work with elemental energies and Lords of the Elements in the Northern and Eastern Quarter that you do not try to pull in Fae and Angels for the other two.
Try to use similar language and structure for each quarter. If you speak formally with ‘thee, thou, art, behold…’ for one Quarter, don’t skimp and say, “I ask you, Guardian of Earth, to join us now.” Do it the same for all of them.
Use the same focus and attention on your calls as you do on your dismissals. Think of it like this — you’re planning a big party and you put all of this time and attention to detail into getting the invitations right, the food set up, decorations, music, games, etc. Then, when it’s all over you barely say good-bye to anyone, leaving them all to wonder when it was you decided to go to bed.
That’s rude to your party guests and it’s rude to your Quarters. If you’re going to take the care to invite them, you should put just as much devotion and attention into bidding them farewell.
Specific — For everyone/everything you invite, you should have clear instructions for what that being is going to do and what purpose it is to serve. If you want the elemental energies to lend their power to your magic, say that. If you want the Lords of the Elements to guard and protect your circle, then say that. It’s not enough just to invite everyone and everything in the universe to your magic show — you have to tell them what they are doing there.
*”I summon, stir, and call ye forth…” is largely the formulae that all other Quarter calls are built from. But it’s important to know which entities are summoned, which are stirred, and which are called.
You SUMMON anything on a low-vibration energy plane or Fae energies, these are the forces of elements or anything that doesn’t have sentient intelligence.
You STIR anything sleeping (ancestors, Mighty Dead, ancient primordial beings who don’t often get the wake-up call to work with us mortal folk)
You CALL anything bigger than you — Gods and Goddesses, dragons (though if they’re sleeping you might try stirring them first), Lords, Angels, Daimons, etc.