1

Start with a guidebook.

Seriously.

2

Hi) this will really depend on your cultural -social life- gastronomic preferences.. But Porto + Douro Valley tour and wine tasting while staying in a palace / mansion (pousada) is incredible..
Lisbon in the best example of 'Old Europe' charm of course. You could stay in old city or in Cascais (Oitavos, Pousada de Cacais, Farol Design hotels) on a ocean side.. to be able to travel around to see amazing monuments
Surely city of Coimbra is extremely interesting too..Ahh, so many! good luck )

3

Hi Rick,

There are so many options and it all depends on what interests you most.

For a focus on historic cities, and winter time is good for this: Lisbon, Sintra and then train up to Porto.

If you want to get out to old provincial towns and countryside, then Lisbon, followed by the Alto Alentejo region, with Monsaraz, Evora, Borba amongst others.

For the coast, Lisbon then down the rugged western Alentejo and Algarve coastline (avoid the central part of the Algarve south coast if you're not into built up touristy areas).

If you're into mountains, rivers, hiking head up to the Beiras (although it's the coldest part of Portugal in the winter and is bound to rain and may snow).

Hope that helps.
There are some region write-ups and places to stay on http://www.hideawayportugal.com/modules/home/home.php

4

Just came back from Portugal myself and had a really great time.

As its Christmas time you may want to factor in weather conditions to decide where you're going, so may want to stick to southern Portugal rather than Northern. I spent all my time in nothern Portugal (my partner's parents live in Coimbra). Can really recommend Porto, we had such a good time there and its a city really trying to push ahead of its southern counterpart while maintaining its amazing cultural heritage. Spend at least two days there.

Could go to Coimbra for the day, but there isn't a huge amount to see there, but its good to soak up the atmosphere. Also went to Tomar, which I loved, the Convento de Cristo has such a great atmosphere and will be relatively quiet.

Factor in where you go by what may or may not be open over the Christmas period.

5

If you want sunshine and unspoilt beaches then come to the Algarve!
you might enjoy my blog post to get you in the mood for an Algarvian Christmas here:
http://algarveblog.net/2011/12/23/the-12-days-of-christmas-portuguese-style/
You will find a much less frantic, more traditional and relaxing pace of life here - and wherever you choose - have a fab time!