One thing you can do to aid in success is decide how you choose to grow your garden. For instance, a lot of hybrid tomato and pepper plants are hybridized to perform well under conventional agriculture methods, and those plants do very well with regular doses of high nitrogen fertilizers that have their nutrients in readily available forms for the plants to use. These plants will grow under organic conditions, but may not thrive they way they were intended. There are also hybrids bred for organic gardening, and one way to find those is to look for OSSI (Open Source Seed Initiative) seeds. Heirlooms can perform well under both growing styles, but sometimes they can have less resistance to diseases than some hybrids bred for disease resistance. Another thing to consider is if you plan to save seeds. Saving and planting a seed from a hybrid will not be the same plant that the seed came from, as the genetics tend to revert back to the parent breeds that the hybrid was crossbred from. Saving and planting open-pollinated heirloom seeds will always yield a plant and fruit that is the same as the parent it was saved from, granted it did not get cross-pollinated with another variety in the garden. There are simple techniques to avoid cross-pollination of heirlooms so you can save seeds that remain true-to-type. In theory, you buy seeds once, and forever grow them year after year. I hope this helps you make an informative decision on what varieties to grow.
Edited to add words open-pollinated.