So, Red Star. Easy to find. Close to the centre, it takes 7 minutes by tram to get there. The rooms are simple, but nice. Clean bedsheet and bathroom.
Staff is extremely helpful and really friendly. They will always find you a way to spend free time. You can also spend time with them at the reception and have a great talk or play badminton outside the building :)
There's no typical common room, but they arranged really nice "common area" next to the reception (great coffee, really good WiFi connection, you can easily download stuff, eg. movies).
It's super cheap, so you can spend more in bars and cafes.
I miss this place somewhat. Hasta la vista Red Star ;)