Wait to wash your fruit until just before you slice it. This will extend its shelf life in your refrigerator.
Fruit salad can be made up to 6 hours in advance. Store it in the refrigerator and wait to add the banana until just before serving. If you plan to add other fruits that will turn brown, such as apples, also wait to add these until just before serving. Restir prior to serving. I do not recommend making fruit salad a day ahead or refrigerating fruit salad overnight if it can be avoided, since the fruit will become somewhat mushy.