1. Ronald Weasley's middle name is Bilius.
2. The name of Ginny Weasley's pygmy puff is Arnold
3. Hufflepuff's ghost is the Fat Friar
4. Hogwarts has 142 staircases
5. The Hufflepuff's dormitory is close to the kitchens
6. Voldemort's first name is Tom
7. Ravenclaw's ghost is the Grey Lady
8. Dumbledore has a perfect map on his knee of the London Underground
9. It costs 14 sickles if you want a hot-chocolate while riding the Knight Bus
10. Hepzibah Smith's house-elf is called Hokey

If you got them all right, I award you 20 house points!