A peaches are either freestone, flesh separates easily from the pit, or clingstone, flesh does not separate from the pit. Freestones are generally preferred for eating fresh and clingstones are generally preferred for canning. I can’t tell the difference from the outside, so it’s always a surprise when you cut into them.
Ripe and mature peaches are firm to slightly soft, and the skin color should be yellow and red. Avoid greenish peaches – they usually don’t ripen properly.
Nectarines can also be either free- or clingstone. Ripe and mature nectarines have bold color and are plump and yield slightly with gentle pressure. Color should be a bright red with orange/yellow. A very hard nectarine should ripen normally withing a few days at room temperature.