The best thing we ever did was to use a 'layering' method for growing an organic garden. Till the original ground, add a 4 inch layer of compost on top and then add a 1-2 inch layer of mulch (branches and leaves) on top of that. Top it with mulch as needed. Each layer breaks down and feeds the original ground where the plants root, while keeping it super moist and creating it's own super-micro-organism system that doesn't get disturbed. Throw in a good crop rotation plan and you're done!