If the resturant has nutritional info online or in a pamphlet that would be your most reliable way to calculate points. Dining Out book says 7 points a slice for papa johns... the domino's section is a bit confusing. And if you have etools there is a pizza "cheat sheet" to help you figure out points on there.
And remember, even if ham and pineapple don't add any points to one slice, if you have multiple slices they may start to add a point or two since the calories are building.
pizza and points help
All you can do is your best! 
