Be sure your oven is preheated before putting the pie in the oven and close the oven door as quickly as possible. A lot of heat escapes when the door is opened. And be sure the rack is in the center of the oven. I always bake my apple pies at 425 degrees for the first 15 minutes, then turn the temp down to 350 degrees until the pie is done.
This is the recipe I use and it is wonderful. The sauce poured over the apples keeps them juicy. The criss-cross lattice top crust allows the steam to escape while baking. If you put a solid crust on the top instead of strips, be sure to make several cuts in it so the steam can escape. The steam needs to escape so the crust will bake properly.
Alabama Apple Pie
5 to 7 Granny Smith apples
1 stick butter
1/2 cup sugar
1/2 cup brown sugar
3 Tablespoons flour
1 teaspoon cinnamon
Pinch of salt
1/4 cup water
1 double crust unbaked pie crust
Preheat oven to 425 degrees. Unroll one pie crust and place in deep dish pie pan. Unroll second crust and cut into 1/2 inch strips.
Peel and core apples; cut in 1/4 inch slices. (If apples are too tart, sprinkle with a tbsp of sugar.) Place apples on crust in pie pan.
Melt butter in sauce pan on stove, add sugar, brown sugar, flour and cinnamon, stirring until blended. Add water and continue stirring. Cook on medium heat until mixture foams and boils. As soon as mixture boils, reduce heat to low and continue to stir for 6 to 8 minutes, until sugars dissolve and mixture thickens.
Pour 3/4 of mixture over apples. Place strips of second pie crust over apples, making lattice design. Using pastry brush, brush some of the mixture on lattice crust until well coated. Pour remaining mixture on top of the lattice crust, allowing mixture to seep down into pie.
Place pie pan on a cookie sheet. Bake at 425 degrees for 15 minutes, then reduce oven temperature to 350 degrees. Continue to bake for 40 to 45 minutes.