I asked the same question on the Soil Forum. Most people said don't use vermiculite or too much compost. I just went with topsoil and two different types of compost and a small bag of lime (like in Mel's mix). Try the Square Foot Gardening forum, since those guys are constantly answering these questions. I will be growing tomatoes and peppers and melons in mine. You do want to make sure that your soil drains well, possibly by adding some sand to your mix.

Good luck! It was nerve racking for me to decide what to put in my box, but I can just add extra nutrients later on if needed. Granny has had success with using 100% Compost.

Here is a link that might be useful: Square Foot Gardening Forum

thanks for pointing me toward the SFG board. My wife is very interested in trying that approach. She wants to do the Mel's mix thing; I've been thinking why mess with what nature already came up with - i.e. topsoil or garden soil + some compost. The SFG board provides much additional info on this topic.

I don't know if what I did was correct, but here goes. I started by tilling the heavy clay soil in my 10X10 framed in garden. I added about 3 standard trashbags of oak leaves, 1 cup blood meal, 1 cup bone meal, 1 cup epson salt, then topped with 2 96 gallon trashcans of green manure (blend of cow, pig, goat) obtained from a local stockyard for free. This was spread out over the leaves in November. Mid January the garden was retilled as deep as possible while adding a bail of peat moss. After tilling one of the local groc store had a sale on shrimp, so I bought 12 lbs. after peeling and deheading I buried the heads/shells as deep as possible (to keep the dogs out) in 4 different places (dug until the heavy clay was too hard to get a shovel into). In Febuary, I obtained 1 96 gallon trashcan of well cured compost from my grandfather, so I added it. March 1st I made my rows, and ended up with 4 2' rows which are about 18" above the ground level. While making my rows, it appears my garden is loaded with earthworms, so I am taking that as a good sign. About a week ago, I planted 1 cherokee purple tomato and a few cucumbers, so far they seem to be thriving. Plan on adding the peppers and the rest of the veggies once night time temp gets to about 65. Now daytime temps are 80 and night time temps are in the 50's. In about a week it should be time to start planting the rest of my garden.

Some varieties like datil and habanero do better in a sandier soil mix that dries out a little between rains/watering. All the C. chinense strains of pepper I've grown seem to do well with that. They do fine in a tall 5 gallon bucket or you can vary the soil mix in one part of your raised bed. C. annuum strains don't seem to do well in that.