My fiancee and I have lived in our current home for a little over three years. Upon moving in, the landlords were kind enough to allow us to build a garden in the front yard since the backyard gets poor light. We did not have much experience gardening, so we checked out a lot of books from the library to being our research. We quickly discovered that many avid gardeners recommend using raised beds to grow food.
So, we took a trip to Home Depot to buy some lumber and galvanized nails, and then we got to work on placing our beds. First, we double dug the area where we were going to place the beds. This means that we dug several feet into the ground in the location where we were to place the bed. This breaks up the soil, and then we added some topsoil to enrich the soil. Once we finished this, we placed the box we had built on top of the newly amended soil. Then, we filled in the bed with more topsoil. We started with two raised beds and now we have six! I highly recommend them, like many other gardeners. Because the beds are raised, it is easier to reach and water the beds. Plus, since you are not walking on the soil, it does not get compacted and the plants have an easier time growing. And since the soil is amended, weeds are far less likely to make their way into the beds. In fact, our neighbors have followed suit and they now have six raised beds in their yard as well.
Although home improvement stores sell pre-fabricated kits for making raised beds, it is so simple to make your own. If you want to get started, I would suggest looking at Rodale's Encyclopedia of Organic Gardening as a reference. Good luck!