Everything you see in Prague is a highlight of some sort, given the beauty of the city. More than any other city I have been to, Prague is consistently beautiful and literally every building is worthy of pictures. Having said that, the things I enjoyed most included:
- Hradcany (the Castle): an amazing site overlooking the city
- Vysehrad and the Slavin Cemetery: an off-the-beaten-path site and the most amazing cemetery I have ever seen
- Staromestské námestí (the main square in the Old Town): a good starting point and fun place to hang out
- Petrin Hill: for the best view of the city
- the amazing architecture throughout the city
- the bridges and statues all over the city
Quick Tips:
Don't try and see every single site in Prague if you only have a few days. My favorite part of the trip was hanging out at outdoor cafes and enjoying the people watching. This wouldn't have been possible if I had tried to see every nook and cranny of the town.
Don't be afraid to hop on the subway and head out of the main tourist center. The subway was easy to navigate and it was nice to enjoy a more local experience.
Bring some good walking shoes and lots of film.
Crystal is a good souvenir and there are several shops where you can find some very nice crystal vases and such. If you don't want to carry your purchases, the shops will ship them for you. You can negotiate the price.
Best Way To Get Around:
Don't worry about renting a car unless you plan on driving outside of the city. It is easy to walk anywhere you would want to see in the main parts of Prague. For perspective, it only took 25 minutes to walk from the castel to the main square (which cover the boundaries of where you will walk most of the time).
For outlying areas, the subway system was very easy to navigate.
When you get a taxi, ask the hotels to call one. If you hail one on the street, it tends to be much more expensive. Make sure the taxi has a meter. In terms of comfort and cost, I found the taxis to be quite reasonable.