I think this is the correct way... see how it's in the same shape as the toilet, and the tab fits perfectly to cover the exposed part of the bowl?
This is Loryn's way... nice and neat, but then you have to pluck the liner off of the seat and put it in the toilet before you flush:
The backwards way (according to me) although it should have been moved forward a little, I think:
And some people don't even bother to pull down their pants before they pee:
Who needs a seat liner when you do it that way?