Celebrate the birth of Jesus.
Go to church.
Enjoy the company of friends and family.
Remember loved ones.
Get a tree, decorate it, have your kitten dive under it, swat at ornaments, climb it.
Decorate your house.
Wear a gaudy Christmas sweater.
Shop for junk, wrap it and give them to people.
Shop for thoughtful presents, wrap it, and give them to people.
Make some presents, wrap it, and give them to people.
Donate money or time to those in need.
Send Christmas cards.
Drive around and look at decorations.
Cook lots of food.
Eat lots of food.
Sing carols.
Go to parties, office or otherwise.
Go sit on Santa's lap.
Count down with an advent calendar.
Leave milk and cookies for Santa.
Or don't. Like Burger King, have it your way.