Most vegetables will grow as well, if not better, in a raised bed as in a conventional garden plot. You can simply mound up the soil into long, flat-topped hills to create your raised beds. Choosing a building material can be tricky. Many people prefer not to use pressure-treated lumber for growing vegetable crops, fearing the chemicals used to treat the wood will leach out. Raised beds made from untreated pine will last a few years but will rot and need to be replaced. "Plastic lumber", made from recycled plastics is another option--perhaps not as attractive but certainly long-lasting. Or, you can use concrete blocks to make a more permanent raised bed.
Once you decide on the building materials, choose the sunniest site available and, if there is existing vegetation, dig the area to roughen it up. It isn't necessary to remove the debris because you will be putting new soil over the top. Then simply lay your lumber or concrete blocks out in a square or rectangular pattern and build up each level, securing the wood together with screws or the concrete with metal posts driven through the top holes.
Fill with a mixture consisting about 3/4 good topsoil, and the other quarter made up of aged compost, well-rotted manure and/or shredded leaves or grass clippings should work well. Depending on the soil type, you may want to add some lime to raise pH, and/or some bonemeal for phosphorus. Some root vegetables, such as carrots, require deep soil, so either make the beds quite deep (24" is minimum) or build them up over existing garden soil. You can purchase top soil in bulk and have it delivered. The more you purchase, the cheaper each yard will be. Best wishes with your new garden!
Q&A Library Searching Tips