Although Willow and Tara are said to practice a form of Wicca, the spells that are used on the show are not real.
To Curse a Vampire With A Soul
Quod Purtitum est in venietur
Not dead, and not of the living,
Spirits of the interregnum I call.
Let him know the pain of humanity,
gods, reach your wizened hands to me.
Bind him, cast his heart from the evil realm.
I call on you gods, do not ignore this supplication!
Let the orb be the vessel to carry his soul to him.
It is written, as it is in my peoples heart to wield,
Let it be so! Now!
-From 'Becoming
To Transform A Person Into Their Halloween Costume
The word that denies thee, now inhabit.
The peace that ignores thee, now corrupt.
Chaos, I remain as ever, your faithful, degenerate son.
Janus, hear my plea.
Take this as your own
Come forth and show us your truth.
The mask is made flesh.
The heart is curdled by your holy presence.
Janus, this night is yours.
-From 'Halloween'
To Imbune The Slayer With The Power Of Three
The power of the slayer and all who yield it, Last to ancient first we invoke thee.
Grant us thy domain and primal strength. Accept us in the power we possess. Make us mind and heart and spirit joy.
Let the hand compass us. Do thy will.
SPIRITUS. Spirit.
ANIMUS. Heart.
SOPHUS. Mind.
And MANUS. The hand.
We enjoin that we may inhabit the vessel, the hand.
Daughter of Sineya, first of the ones.
We emplore thee, admit us.
Bring us to the vessel. The Hand.
-From 'Primeval'