Toss the slices with a little lemon juice
Use pineapple juice or orange juice instead of lemon juice
Soak the slices briefly in salted water, then drain
Soak the slices briefly in honey water, then drain
Keep the slices submerged in cold water until ready to serve
Store the slices in an airtight container
Press plastic wrap directly onto the cut surfaces
Refrigerate the slices immediately
Use an apple-preserving product with ascorbic acid
Cut the apples just before serving
Choose firmer, fresher apples
Keep the slices away from air as much as possible