Christmas is perhaps the year's major event in the strongly catholic countries of Southern Europe and Latin-America. Catholic countries recognise the 24th as the day of Christ's birth of December and start celebrating on that day, not on the 25th as here in the UK.
On the 24, the family will gather to celebrate and eat snacks. At midnight, they will attend the misa de gallo which celebrates the moment of Christ's birth. After this mass, at 1am, they return home to Christmas dinner and the opening of the presents.
The celebrations are not limited to Christmas Day but start on the first of the month. You will see people out on the streets singing aguinaldos, roughly equivalent to our Xmas carols. The Latin-American aguinaldos are closely related to the Spanish ones, with some rhythm changes, except in Venezuela, where they have evolved a huge repertoire of their own. Next time you see a group of people out on a freezing December evening in Aberdeen, apparently serenading someone in a house, accompanied with maracas and a cuatro (traditional 4-string guitar) , you'll know what it's all about!
In Spain and Latin America, the focus of Xmas is firmly on the Christ child. Indeed, it is he who delivers the presents, not "Santa Claus" (an invention of the English in colonial New York, based very loosely on Saint Nicholas).
Every household will have a pesebre (manger display), with all the usual characters in miniature.
In Venezuela, a neighbour will "steal" the Christ child figurine, a reference to Herod and the slaying of the children, placing it next to their own. The victim household will then organise a house-to-house search, with lots of songs, and, on finding the culprit, will symbolically punish him.
As here, Christmas is a time of merriment and feasting. You can get some of the traditional Latin American dishes, specifically Hallacas, Pan de Jamón, Jamón Planchado (sort of gammon steak with pineapple) and Torta de piña from La Paella.
For more information on Christmas in Latin-American countries, we recommend the site Navidad Latina.