Main tourist areas include ---
the Old Town Square, with the Prague astronomical clock. https://www.pragueexperience.com/places.asp?PlaceID=594
The Jewish cemetery, located in the Jewish Quarter, near the Old Town Square. http://www.prague.cz/old-jewish-cemetery/
Charles Bridge https://www.pragueexperience.com/places.asp?PlaceID=598
Prague Castle http://www.prague.cz/prague-castle.asp
This is just a brief mention. Any of the restaurants/pubs we found to be great. Prague is very cheap to eat and drink! Also, taxi's are very cheap.
For a day trip, there is Sedlec Ossuary, if you like bones, churches, and cemeteries, in Kutna Hora, a short train ride away. And if you go there, a great restaurant is Dacicky Pivnice, located a short walk or cab ride away from the ossuary. Has been reccomended in this forum, and I have been there myself!
Don't know anything about the Prague card, never got one or needed one.