I like a combination of fine redwood bark (sold as mulch), home made or bagged compost, and clay cat litter or Napa Aui\to Parts Oil Absorbent (part #8822). You can read more about the mix on the container forum. Roots grow best in the intersection between water and air and a chunkier mix with good water retention encourages healthy root growth and everything else follows from that. I kind of stumbled into the mix of chunky stuff years ago. For years I used chopped garden waste along with compost and clay cat litter, but getting the right mix of garden waste that would last an entire season without completely breaking down was always hit and miss. Then I stumbled on Al's information on the container forum and the redwood bark which is cheap here in California turned out to be a great replacement. I've just started experimenting with the Oil Absorbent in place of cat litter. The peat moss and vermiculite additions are not very useful although they are traditional. The peat moss is hard to wet and doesn't provide for the light, porous mixture that promotes root growth (and is not a sustainable choice, either). The vermiculite breaks down very rapidly so that it provides little value and is quite expensive to boot. Additionally, I dump leaves and clippings between the plants to compost in place and dump kitchen waste into small holes that I make in random spots. My tomatoes grow to about 14-16 feet tall (there's a pergola overhead for support), so I must be doing something right. Here is a link that might be useful: Al's Container Soil

Let's consider two issues in turn: what kind of soil, and then how much. The quality of your produce is directly related to the quality of the dirt they grow out of. This makes sense, because plants consist of energy from the sun, oxygen and carbon from the atmosphere, and matter from the soil in which they live. Therefore, it is worth your while to make sure that your beds are full of good dirt. You want to pay attention to a few factors in garden soil, mainly nutrient content and drainage. Once you know what you want, you can buy cheap ingredients and mix them to get what you desire. Base: good ol' dirt A good base for a garden soil mix is the cheap topsoil that you can get at your garden center. Lots of stores sell topsoil for cheap in the spring, like maybe $2 or less for a 40-pound bag. That seems like a lot of dirt, but it's really a negligible amount once you start filling in your bed. Nutrients: compost & peat moss You also want to have a lot of nutrients, so it is a good idea to add in some compost. It's great if you're making it, if not they sell it at garden stores. It's incredibly rich, so it's okay to mix in only a bag or two per raised bed. Peat moss is also a good idea, as it is full of organic matter. It comes in big bags, and is really concentrated so you don't need all that much to have an effect, maybe half a bag for a medium-sized bed. Drainage: sand/vermiculite & peat moss You also need drainage, which refers to the ability of water to seep out of the topsoil. (This is what distinguishes a swamp or marsh from "good" land where you can grow things like tomatoes or corn.) This is aided by little holes in the soil. Since water seeks the lowest level, raised beds inherently have good drainage, but you can make the situation even better. It's a good idea to break up your substrate (the area under your bed) pretty well with a fork or spade before building your bed. You also want to make sure to mix in your added soil with some of your substrate, because an abrupt border can lead to problems with compaction: sometimes roots will never penetrate the substrate if it's not mixed, and drainage will be reduced. It's a good idea to mix some sand into your bed's soil to increase drainage; vermiculite (the white chunks in potting soil) also works, but then it looks too much like potting soil and not enough like a garden for my tastes. The light texture of peat moss can also aid quite a bit in creating better drainage, in addition to the nutrient benefits. That said, it will take a LOT of dirt to fill your raised beds. I built some beds that are 5' wide, 10' long, and 1' high. Each one required a bag of peat moss and 1,600 pounds of topsoil! That's 40 bags of that cheap topsoil, which even at a low price came out to hundreds of dollars for a few beds. I highly recommend against using potting soil or your bill will easily stretch into the thousands of dollars. The way to do it on a budget is to: 1) buy cheap materials 2) mix it yourself 3) use topsoil that is on sale, or maybe even free from a local landfill 4) you can even fill the bottom with straw: a straw bale is pretty cheap and gets you a lot of organic matter. It will biodegrade in a year or two if it's buried at the bottom of your bed, it will increase drainage, it will not hurt your plants, and it's a lot easier to move than dirt. In Scandinavia, they traditionally grow potatoes in straw without even any dirt, and they do fine (plus then they come out totally clean!) 5) don't use potting soil! unless it's old potting soil that you have tossed in your compost pile or something I hope all that helps -- good luck building! Also, it might be a good idea to line the bottom with chicken wire or hardware cloth if you have problems with varmints in your area (so they can't dig up into your bed), or to line the bottom with landscape fabric (to prevent grass etc. from growing up into your bed)

I second Mandolls method, and the corner stake idea to aid in leveling sounds like a great idea. When you have a single bed by itself, it looks just fine if it's a little out of level. But in my opinion, as soon as you start placing several beds together, it starts to look a little sloppy if they're all at different heights and degrees of level... simply because your eye can easily compare one bed to the next. Along those lines... it's all about what pleases your eye, and just "eyeballing the degree of level is fine. If level is very important, it's easy enough to use a level to aid you. Start by laying the beds in the location they're going to live. Once you've kicked them around into an arrangement that suits you, start at the highest point of your slope and level out from that point. You'll basically be lifting the down slope edges of the beds until the level looks right. Eyeball across adjacent beds to align them and put some sort of shim under them to hold them at the appropriate height. (Or utilize Mandolls stake technique) Once you've tweaked everything to a point that it pleases your eye, you should have created a series of wedge shaped gaps under your bed walls. Measure the height of the gaps at each end, transfer them to a board, draw a straight line between them, and cut the "wedges" preferably with a circular saw. Nail/screw these tapered pieces to the underside of your beds and you'll have a neat, organized looking arrangement of level beds for years to come. Having said all of that... If the gaps are only a couple of inches, you could simply shim them up with a brick or a small rock rather than taking time to do some carpentry! I apologize if I oversimplified the instructions not knowing your skill level. Best of luck!

My daughter is in 4-H horticulture and one of her projects is with stock tanks. You take two 2 1/2'high x 4' long stock tanks put them together length ways. Make sure they have holes in bottom so you can put a screw drain cap on them. Build with treated wood a 4'high x 8'long box to surround theses tanks. make sure you drill a hole where the drain cap is. Put a 4'width x8'length lattice on top of tanks.Take a pvc pipe put through one of the lattice holes and into to tank about an inch. Then hook a pvc elbow and another pipe so it comes out of the side of the box. (You will have to drill another hole) On top of lattice cover generously with straw and then cover straw with dirt to the top. Fill the water tank through the pvc pipe until water comes out. Plant your garden and watch it grow. The warming and moisture from bottom grows a wonderful garden. It is an experiment that turned out Great.