Spread cheer. When you hear Christmas songs, instead of being grumpy (ever heard of Ebenezer Scrooge?) smile and whistle along. Being cheerful during the Christmas season really will help in spreading Christmas spirit to those around you, plus it helps you enjoy it more too.
Wish others a Merry Christmas if you know they celebrate Christmas. If you’re not sure, just say Happy Holidays! Either way, you are spreading the holiday cheer.