Soft fruit is picked when it starts getting soft. Baring that pick when the background color turns from white to yellow. This works with some peaches. Asian pears are picked by color and taste. Other pears are picked when the seeds turn brown or by date and ripened off the tree. Apples are picked by color and taste. Many fruits can be picked by calender date. My Gala apples are usually ripe in early August. Grapes are picked by color, taste, and date depending on variety. Blueberries are usually picked after they reach a full blue but I've carried them many wks longer sometimes to good effect and sometimes not.

The Fruitnut

The Fruitnut is right. I start tasting my fruit when it is tennis ball size. If it does not taste good then I wait a few weeks then taste again. Here in the south we eat plums, apple & pears green as well as ripe. Test for yourself you may like the different stages of green & ripe.
Berries I eat based on color.