The type of apples you're baking with determines the amount of sugar to use in your filling. Since Granny Smiths are more tart than Golden Delicious apples, for example, you'll want to use an additional 1/4 cup of sugar.
Fruit pies are done when the crust is golden brown and the filling is bubbly. As an extra test, gently pierce a knife through the crust into an apple slice or two -- the fruit should be tender.
Let fruit pies cool at least two hours before cutting them. That way the slices won't fall apart.
To prevent the edges of your piecrust from overbrowning, fold a 12-inch square of foil into quarters, then cut a 7-inch circle out of the center. Unfold the foil and mold it loosely over the pie's edge.
Cut several slits into the top of a double-crust pie before baking it to allow steam to escape and to prevent excessive bubbling.
Watch our test kitchen chefs make a pie with a lattice top HERE