Many people think that you need to plant all of your crops early in the season, but for many shorter season crops (e.g. greens, beans, herbs and root crops) you can continusouly plant, and enjoy crops throughout the season in order to maximize your harvests.
To have a continuous supply of these crops you can plant them every 2-3 weeks throughout the season. Particularly with root crops, you can plant them next to one another so that when you pull out one harvest, the next one can grow into the space.
Consider the length of your growing season (know your frost date!)
Know your fast growing vegetables (radishes, greens, peas, beans)
Think about crops that finish early, and what you can plant after they are done.
E.g. If you are growing garlic, it is generally ready in late July, once you pull it out, you will have space in your garden to let other large crops like tomatoes fill into, or open space to plant new successions of crops like lettuce.
Some more information from the Farmers Almanac to help guide you including a chart and video
Head photo credit and some more great tips: Mother Earth News