How do you earn points?

You earn a percentage of all giveaways created by members as points up to a maximum of 300.

Can't remember the percentage though...

From the FAQ:
The point system is designed to prevent users from entering for every single giveaway. This lowers the overall number of entries, and provides everyone with better odds of winning games they're interested in playing. New users start out with 25P. Every time anyone submits a game, every member of the site, excluding the giveaway creator, receives 5 percent of that gifts value (in USD) in points. For example, if a $50 gift is created, every user on the site receives 2.5 points. And, if a $20 gift is created, everyone would receive 1 point. These points can then be spent on entering giveaways.
1P = $1 - When entering a giveaway, 1P is equal to $1. If you're entering for a chance to win a game valued at $20, you'll spend 20 points. If at anytime you decide to remove your entry while the giveaway is open, those points will be returned.
The maximum number of points that can be banked is 300. This is to prevent users from stocking up on points while being away for long periods of time.

you must sacrifice a sheep