Toss the slices with lemon juice
Soak the slices in cold water with a little salt
Soak the slices in cold water with a little honey
Use ascorbic acid or vitamin C powder
Keep the slices submerged in water until serving
Store the slices in an airtight container
Press plastic wrap directly against the cut surfaces
Refrigerate the slices promptly
Slice the apples just before serving
Use a commercial fruit preserver
Choose firmer, fresher apples
Coat the slices lightly with pineapple or orange juice