If you are not sure, look for All America Selections award winners or other such superlatives that have been tested in many regions of the country. Plant at the proper depth. It's easy to set transplants too deeply. If you do, stems may rot. Use your trowel to make a hole just deep enough so that the top of a transplant's root ball is level with the surface of the ground.
Tomatoes are an exception.
They may be planted deeply and will sprout roots along the stem, but remove the lower leaves first. Fertilize hybrid vegetables regularly. Hybrids are bred to perform their best with proper nutrition. Water vegetables regularly. Vegetables need plenty of water to develop proper size and flavor.