A winter holiday in Poland- where do I begin?

21 years old, American girl taking a 3 week holiday to Poland in February 2015.

I've never been before, I have no idea where to start my itinerary!

I know it will be cold. But seriously, like it can't be any worse than where I live. Really, our winters are fierce.

What are the best cities to visit? What should I do or see while I'm in these cities? What are things to do and see in the middle of winter?

Best food? Best places for shopping?

Most efficient way to travel?

Any cultural things I should know before I go?

I believe I am flying into Cracow. So that's where I'll be first.

Xoxo,
Andrea

I would travel by trains marked in RED on Railway staition timetables.
They are fast trains. Cost a bit more, but you will be in safer company. Itinerary, apart from Krakow and Gdansk , I would put Torun and Gniezo. The former being the home town of Kopernik, and the latter being the oldest city of Poland.

Warsaw the capital is a must, Gdansk is amazing and Kraków is intersting if very very touristy and in my opinion overrated, especially compared to Warsaw and Gdansk. Torun is worth a visit. Gniezno is nice but nothing special - just a small town with an old cathedral. You might like Bialowieza forest and Hajnowka with lovely wooden houses and onion domed churches. Małbork castle (conveniently between Gdansk and Torun/Warsaw) is spectacular.

Sylvio is right, trains are best and use the intercity ones which are more comfortable though still relatively cheap.

ski=ing in Zakopane?

Hey jon357,"...Gniezno nothing special"...Ouch!

I was born 10 miles from there!...;(
Right as you are, though, one gets a good flavour of a regional market town, relatively unspoilt by PRL architecture, and just small enough for a walk, without the racket of trams, or multi-lane motorways.;)

It's a nice enough place but only really worth a look if it doesn't involve a detour. Torun is good though and Poznań has good architecture. Everybody hates £ódź but that has charm and a visitor from the U.S. might find it interesting.