As much house points as you want- First you have to be at Hogwarts.
Then, when you are at Snape's first class, and he asks you to get the ingredients, go to Professor. Sprouts' greenhouse (go out the front door of Hogwarts and turn left).
Then, kill a monkey-like thing or snake, talk to her. She will say, "Well done Harry, I am awarding 1 house point for pest control". Then go to Hagrid's Hut (directly south of the greenhouses).
Talk to Hagrid, then go back to the greenhouses and talk to Pro. Sprout without fighting any creatures, and she'll give you another house point.
You can keep doing this as long as you keep talking to Hagrid for as much house points as you want!
NOTE: If you want a lot of points, this will take a while.
Added by: Anon , ID#167