Wait until just before you are ready to serve the salad to slice the apples. They will turn brown if sliced and held too long before adding to the salad. If you need to slice and prepare the apples hours before serving use a water bath made of 1 cup of water mixed with 1 tablespoon of lemon juice. After you slice the apples soak them in the lemon water for 3-5 minutes then remove and rinse them.