Tempting as it is, try not to just buy and plant. To have a successful vegetable garden you need to give it some thought ahead of time.
When planning your garden consider the site, varieties, where they will go, and when you'll plant. Be realistic, only plant what you can maintain with harvest you can use. It is too easy, especially in the beginning, to start too large.
A successful site for most vegetables, especially fruiting ones, should get at least 6 hours of direct sun a day, either continuous, or total from morning and afternoon. If you don't have a sunny site, consider leafy crops such as lettuce and spinach that can get by on 3 to 4 hours of direct sun a day. Root crops such as carrots and potatoes need a bit more light, 4 to 6 hours a day, to have some growth.
Another important site factor, and one you can work around more than light, is the soil. A rich, well-drained loam is ideal but many aren't fortunate to have this at the beginning. If it is clay or sandy, add lots of organic matter such as compost each year in the spring prior to planting. If it is clay, poorly drained, or quite rocky, you might want to consider building raised beds on top and filling with a good soil.
A flat site, or as near as possible, is best. Otherwise it can be hard to work on, and rains can lead to erosion.
Accessibility of the site is important in three respects. It should be close to home, otherwise "out of sight, out of mind" may apply. If you don't visit the garden daily, or frequently, you may miss pest outbreaks and fruit that is ready to pick. The site should be accessible to a source of water. The site should be accessible as well by cart or even vehicle. If you need to bring in a load of compost, soil, or mulch, or remove debris, how will you access it?