There are at many things to consider when choosing your vegetable gardening layout. Since all plants need sun, the positioning of the garden to expose the most sun to the sun-loving plants while providing a little shade for those that easily burn is a very important element of your vegetable garden. If you choose to have plants that love a little more shade but your garden is in full sun, place the taller plants in a position to help with the shading of the more tender vegetation - especially during the hot afternoon sun.
Another thing to consider is the availability of water since ALL the plants in your vegetable garden will need this key element. Make sure the vegetable gardening layout is situated with easy access to your water source, but not in a place that will wash out should there be a drenching rain. The closer and easier your water source is to your garden, the better chance you (or your helpers) will have of being consistent with watering chores. This can be achieved by close proximity to a water storage facility, such as a pond, or should be easy to get to with a garden hose should you need to hook up to a household water spigot.
When choosing where to plant the seeds or seedlings that you would like to put into your vegetable gardening layout, keep in mind that some plants grow much better when planted next to certain other plants. Learn a little bit about what pests you will be dealing with in your particular area. You can plant certain vegetable plants together to help keep pests at bay, such as planting marigolds next to your tomatoes to help control certain aphids and worms that dont care for the smell of the marigolds. There are many combination of plants that you can plant next to each other for this purpose. However, there are many plants that cannot be planted next to each other if you would like to have any vegetables develop from those plants! The key is to learn about the plants and conditions peculiar to your area of the country.
The real key to your success with your vegetable gardening layout and how productive it will be is to know what you want to grow, where you want to grow it, and how all the plants in your garden can be beneficial to each other. This information will make your gardening experience much easier and much more fruitful come harvest time!