Yule is the first minor sabbat of the year, celebrated at Winter Solstice (which is on December 22nd in 2015), the longest night of the year. This day marks the return of the sun, as the days will start to get longer again from here on, and the rebirth of the Horned God, as well as the beginning reign of the Oak King, taking the Holly King’s place and bringing the light half of the year.
This is a day for introspection, peace, planning for the future and new beginnings and spending time with your family and friends. Parallels can be seen in Christmas, Hannukah and other festivals around this time of the year, all with the same motifs: light and joy. Giving gifts and decorating a Yule tree (I decorate mine with candied oranges and other handmade decor!) are popular activities, as is creating a Yule log and burning it in honour of the sun returning.
Other activities include caroling, wassailing, kissing under the mistletoe, making wreaths, storytelling, sending greetings, lighting a fire, as well as charity, donating food and clothing, volunteering or putting up bird feeders.
Edit: It’s that time of year again! I’ll be reposting this for the upcoming Sabbat but will probably be updating it as I go along. Not everything at the bottom is a link yet but the ones that are there should work. If you guys find any problems just let me know!