Music: lots of Christmas carols, So Here it is, Merry Christmas, It’s Christmas, etc., etc.
Food: a very nice dinner. We did have turkey, but you don’t have to. Goose is more traditional, but turkey became more fashionable. You could even have a pie. There should be booze, ale or something. Some sort of dessert or pudding (we had stollen).
Poetry: There’s that poem by John Betjeman, which I quite like.
Decorations: as applied on Christmas Eve plus candles.