Brush or toss cut apples with lemon juice, lime juice, or diluted citrus juice
Store them in an airtight container
Keep them refrigerated
Submerge slices in cold water with a little salt or lemon juice, then drain before eating
Use an apple preserver or ascorbic acid solution
Wrap tightly with plastic wrap if no container is available
Keep the slices away from air exposure as much as possible
Cut apples just before serving when possible
Store only fresh, unbruised apple pieces
Eat within 1 to 2 days for best quality