What usually goes on at a Pagan ritual?

While each ritual has its own unique character, much like a service at Wildflower, there are certain elements that are consistent.  Here is a sample "order of ritual" that give a fair idea of what goes on.

Following is a step by step process for performing your ritual.  Some traditions vary the order in which these steps are undertaken; go with your personal preference or what seems most appropriate for the work at hand.  We've also put together some sample chants below you can use in some of these steps.

Purify Sage, saltwater, sounding or incense are used to cleanse your body and mind, and the space where you will have your ritual.

Ground Tree of life meditation, yoga, drumming, breathing, sound, movement.  Anything that allows you to let go of distractions or stressors that keep you from fully participating in sacred space.  Connect to the earth's energy.

Cast the Circle Use an athame, crystal, finger, sound, visualization to define your own sacred space and help to focus energy.  In each direction, draw an invoking pentacle in the air with one of these tools.  When casting the circle, make sure to return to the direction where you began and ground the energy in the center when you finish.

Invoke Directions/Elements Call in the east/air, south/fire, west/water, north/earth and center/balance.  Use words, movement, song, physical manifestations (i.e., dip your fingers in water to invoke west) or drums; whatever you are comfortable with.

Invoke Goddess and God Pick an aspect of the Goddess and/or God that suits the work for the night.  Some traditions only invoke the Goddess (Dianic Wicca); others invoke both; others invoke non-sexed identified spirits or forces.  Invoke the aspects of deity that suit your purpose--a goddess of justice such as Athena for a reversal spell, a god of the forest for protecting wild areas near your home.  Invocation can be through spoken word, silent meditation, dance, song or any other way you choose to invite deity into your sacred circle.

Complete the Work Every ritual should have an intent.  World peace, personal healing, spell work, celebration of a holiday or moon phase, meditation, initiation, etc.  This section of the ritual can take the form of a craft, a meditation, or a poem/written statement.

Raise the Cone of Power Drum, dance, sing, visualize energy to energize your ritual work.  Works best in groups when there is an agreed upon visualization or intent.  Focus the energy towards your intent to make your wish a reality.

Devoke Make sure to thank and send away the energies that you invite.  Generally done in the reverse order that you invoke, i.e., thank and dismiss God, Goddess, elements, open circle.

Eat It's very important to eat something after ritual to help you ground after working magickal energy.  Bread, cheese, or crackers are great--and make sure to have them ready before you start your ritual!

Casting the Circle
By the earth that is her body
By the air that is her breath
By the fire of her spirit
By the waters of her womb
As above, so below,
The circle is made whole.

- Traditional

Opening the Circle
The circle is open, but unbroken
May the peace of the Goddess
Go in our hearts
Merry meet, merry part
and merry meet again!

- Traditional

Source: http://witchonthego.com/structure.html