For information about Yule, read the article Satanic Holidays.
I would recommend that you celebrate Yule on 21 December if you are a Satanist, or on 22 December if you are a Demonolater.
If you are celebrating Yule alone, I would suggest to do the following:
First, clean the house. It is an important night. Then decorate a tree. The Yule tree should be decorated with Satanic Symbols and Demonic sigils. At the top of the tree I would place the sigil of Satan.
A ritual to Belial is to be held this night. Also purification rituals and re-consecrating the ritual chamber and tools can be done at this time. If you wish to do that, do it before the ritual for Belial.
To begin the ritual to Belial, prepare the altar which must face the North most point of the ritual chamber. At each corner of the altar there must be candles of green or brown color (Belial’s color). In the center of the altar there must be the sigil of Belial. The bowl must also be present in which earth and snow are to be put in.
Sigil of Belial from Goetia
Sigil of Belial from Dukante
The practitioner enters the room lighting all the candles and incense (if available) and calls upon Belial with the invocation knife/sword. If he wishes he may use the enn (Lirach Tasa Vefa Wehlc Belial) or personal invocations.
Example of invocation:
“I call upon our god Belial to attend this rite in the night of Yule, the celebration of winter. This sacred event I dedicate in the honor of Belial, our Lord. Let us join in celebration!
Come, Belial, bestow upon me the strength of your design.
Come, Belial, and join me this night to harness the power of the Winter Solstice, a time for cleansing of that which fosters failure and weakness, and a purification of that which strengthens.
Come, Belial, lets celebrate this night in the honor of thy name!
Hail Belial! ”
After this invocation the practitioner places the bowl in front of Belial’s sigil, fills it with snow and soil and speaks the following:
“Let this snow melt as the negative energies around me melt this night! When the earth is clear so will be my soul! ”
The practitioner puts the bowl over the candle flame and waits the snow to melt.
After this the celebrant then gets into prayer to Belial asking whatever he wants to follow after the winter.
Now you may give a closing to your ritual as such:
“I thank thee Lord Belial for attending this ritual. I bid you, go in peace!
Hail Belial, Lord and Master of Earth!” (earth as an element not planet)
After this the celebrant may prepare a meal and eat it with his family.