Buy plants young in the nursery.
Older plants have trouble adjusting to transplanting.
To lessen transplant shock, transplant only in the evening, and water thoroughly. Make and use cutworm collars during the spring. Start summer seeds indoors and move them outside as soon as they sprout. This eliminates the uncertainty of germination, at the expense of a couple of weeks of transplant shock recovery. Planting vegetables at the minimum recommended spacing decreases yield per plant, but increases yield per given area.