Hang around 12 Grimmauld Place and you'll notice the Black family house-elf, Kreacher, peering through the curtains.
28. You Enter Diagon Alley Through A Wall, Just Like Harry
Similar to the way Hagrid introduced Harry to Diagon Alley in Harry Potter and the Philosopher's Stone, you too enter Diagon Alley through a brick wall. If you listen carefully, you will hear the sound of the bricks parting allowing you entry.