To begin with, create a bed with a minimum of 12 inches of good soil. This 12 inches should be a mix of 50% organic matter and 50% good gardening mix. It's a little pricey to get started, but a properly prepared bed with good soil will save you tons of labor and provides instant success. And in subsequent years, it's simply a matter of amending the existing soil. You don't have to start from square one. Most local landscape companies will deliver soil to your back yard.
My beds are already well established and I do have good soil. So when I prepare a bed for new planting, I simply add organic matter.
The first thing I do is clean out all the weeds. Since I've mulched it pretty well when I put the bed to "sleep", there aren't many weeds to remove.
Next I pull out my trusty Mantis Tiller/Cultivator. This thing is great. It's small, lightweight, easy to use and reliable. I can't imagine gardening without it.
Adding organic matter is next. I use Ladybug Soil Revilalzer Compost mix. I love this stuff. It's a mixture of hummus compost, composted cow, turkey and horse manure, granite sand (a small amount to mineralize and improve drainage), and humates for long term, slow release of humic acid, which stimulates microbial activity. This mixture is organic and contains no bioSolids (sewer sludge). It's made in Austin.
My beds are 9' x 5' and I add 4 bags each and every time I prepare a garden bed. The general rule is to spread 2" over the soil and till to a depth of 6-8". For heavy clay soils, 4-6" of organic matter can be added.
I rake the mixture evenly over the bed and till it in until the soil is loose and well aerated.
I made an exciting discovery as I was working the compost into the soil...the bed was full of earthworms!...big and squirly! I was so happy to see that. Earthworms are a sign that your soil is healthy and full of organic matter.
After the compost was well worked into the soil, I raked it one more time and that's it...I was done.
Isn't this beautiful dirt? Like I said, I love dirt :)