For those of you not familiar with Seinfeld, Festivus was a holiday created by the character Frank Costanza as an alternative to Christmas. Mr. Costanza was fed up with all of the religious and commercial aspects of the traditional holidays, and thus, Festivus was born!

[edit] Steps

Set Up your Festivus Pole. Set up an aluminum pole in your living room. It requires no decoration, and has a very high strength to weight ratio.
Celebrate Festivus on December 23rd. You need purchase no expensive gifts. Just invite your family and friends over for a nice dinner.
Air Your Grievances. Tell everyone at dinner how they have disappointed you over the last year. Be sure to include specific details. Have your grievances prepared prior to the celebration. There is no need to make up or hug after the Airing of the Grievances.
Practice the Feats of Strength. After dinner (and dessert) proceed with the Festivus Feats of Strength. "Festivus doesn't end until you pin me..." Remember however, that a participant is allowed to decline on the grounds that s/he has something better to do (which includes pretty much anything.).

[edit] Tips

Feats of Strength suggestions: If you don't want to have to pin someone, consider Thumb Wrestling, Rock, Paper, Scissors, Staredown.

[edit] Warnings

Be careful not to injure yourself or anyone else during the Feats of Strength.
Keep the pole away from all sources of electricity. Aluminum, like all other metals, is very conductive and you may get electrocuted.