The number one factor when deciding what to grow is the amount of space you have. Here's a list of popular vegetables and type of space they're best suited to:
• Small Gardens (multiple medium to large pots on a terrace or roof deck): Lettuces, peas, spinach, herbs, beets, carrots, and radishes.
• Medium Gardens (small section of a yard with a bed of soil): All of the above plus kale, Swiss chard, broccoli, bush beans, onions, leaks, and bok choy.
• Large Gardens (more than one bed of soil): All of the above plus tomatoes, peppers, eggplants, zucchini, and cauliflower.
• Extra Large Gardens (multiple large beds of soil): All of the above plus winter squash, melons, and pumpkins (which need 30-36 inches between them).
Note: There are always exceptions to the above. If you love tomatoes and only have a small terrace, for instance, you may choose to just grow tomatoes. That said, if you grow butternut squash in your small garden, you might only have one plant.