Slice your fruit with a sharp knife, as per your preferences. The fruits can be halved, cut into slices, or diced into small cubes. It is also essential to ensure that the knife is clean and free from rust, which, in fact, can be counter-productive as it tends to speed up the oxidation process.
Place the sliced fruit in a mixing bowl. Do not bunch too much fruit into a single bowl, and if you plan to make a salad, keep the varied types of fruits separated in different bowls, and combine only when you are ready to serve.
Cut a lemon in half, and squeeze the juice over the sliced fruit. The amount of lemons used should be proportionate to the amount of fruit you have. The key is to lightly coat the fruit in lemon juice, not drown them in it. Care should also be taken in order to ensure that none of the lemon seeds make it into your fruit – for this purpose, you may use a lemon squeezer, or simply use your hand to prevent the seeds from falling into the bowl.
Toss the fruit in the bowls with a pair of wooden spoons, in order to ensure that it is evenly coated with the lemon juice. The mild citric acid in the lemons will counteract and prevent the oxidation process.
Cover the bowls with plastic wrap to further preserve the freshness, and place them in the refrigerator until you are ready to plate up and serve.