How do you choose among the hundreds of varieties available, and which crops to grow? The first consideration is what you and perhaps family like to eat. Even if a crop is trendy or popular, if you don't like it and wont eat it, why grow it?
Most crops have some, often many, varieties. These are particular types or selections with certain characteristics such as fruit size or color. There are some terms you may see in variety descriptions.
A hybrid is a plant resulting from the crossing of other parent plants. Since you need these parents to make seeds of the hybrid, sowing seeds of hybrids wont give you the same plants. The other main group is the open-pollinated varieties, or those that pollinate each other in the field. They may not be as consistent, with all the traits of hybrids, but you can save seeds of these and get similar plants. If a variety is open-pollinated, and at least 50 years old, it may be called an "heirloom".
When choosing varieties, look for ones adapted to your region. This may relate to ripening time, or "days to maturity", one of the key factors I look for in my northern garden. A great variety for warm climates, perhaps one you grew up with, may not ripen in time in a short northern growing season. A warm climate crop such as okra, for instance, has some varieties better suited to cooler and shorter northern seasons.
A couple of cultural factors to consider in variety selection are disease resistance and plant size. Some varieties, tomatoes being a good example, are resistant to certain diseases. These are often labeled in descriptions with letters and a key, such as TMV for tomato mosaic virus. The more letters the better! Plant size relates to your site, and where these will be planted.