Drying is the oldest method of preserving food, and certainly the least expensive!
By removing most of the moisture you also remove most of the opportunity for micro-organisms to grow. This prevents spoilage without the addition of large amount of salt or sugar. Some fruits will darken during the drying process indicating oxidization - which implies some loss of flavour and nutrition. Sulphiting prevents this but the safety of sulphites cannot be assumed for everyone which is one good reason for drying fruits naturally. (Beware: sulphites occur naturally in many dried and fermented food products)
To air or sun dry: Spread uniform slices of fruits or vegetables on a clean tray and cover with cheese cloth (to keep insects off). Turn food once a day until it has lost most of its moisture. Fruits should be chewy… but vegetables are usually crunchy when dried.
To oven dry: Be sure your oven can maintain a temperature of 140F or less. Higher temperatures will cook rather than dry the food. Leave the oven door ajar a few inches and set a fan in front of the oven to circulate air across the open door. Turn food often and keep it spread in a single layer. Drying times vary, so pick pieces out as they arrive at doneness.
Try berries, seedless grapes, plums, apples, peaches, pears… even sliced melon… and carrots and zucchinnis are great!