Ondrej's apartment is an excellent option to stay in Prague, is near of everything, and it has the necessary things to enjoy Prague. Also downstairs is the Hostel, and you can share with the people who is staying and have the both of the two worlds, have a private room and meet new people from others countries. Was a really nice experience.
When you arrive, prepare to receive the best tips to know the city, with open eyes and ears, because is a lot of places an things to do. I highly recommend the free tour, you get to know the main places and also the history behind them, also the hostel activities are very good.