Look for fruit with smooth unblemished skin. Avoid extremely hard or dull coloured fruits and soft fruit with soft, wrinkled skin.
Nectarines are simply a fuzzless variety of peach. Nectarines will sometimes appear on peach trees, and peaches sometimes appear on nectarine trees!
Ripe nectarines are fragrant and give, slightly, to the touch.
Nectarines keep for 5 days if stored in a plastic bag in the coldest part of your refrigerator.