For a fluffy and generous meringue: Use 3 egg whites for a 9 inch pie.
Beat the egg whites until they're stiff before adding any sugar.
The egg whites should become glossy on top.
When they're at this stage, if you invert the bowl that the meringue is in, the meringue should remain in the bowl and not fall out.
After the egg whites have become stiff, fold in the sugar gradually. Use a gentle folding motion. Do not beat in the sugar or you'll deflate the meringue.
When it's ready to top the pie, be sure to seal the pie's top completely (from edge to edge) with the meringue.
A good way to do this is to place all the meringue in the center of the pie, then, with a spatula, spread it evenly toward the pie's edge to seal the edge..
Bake the topped pie at 350. for 18 minutes or until the meringue has browned.