If you listed all the true reasons why gardeners run aground, inadequate soil preparation would probably rank near the top. Everybody wants to talk about their new house design, the rooms and the furniture. Nobody wants to worry about its foundation. And so it is with gardening.We're at the lead end of the planting season, so it's the perfect time to jot down pointers for getting your soil ready. Let's start with the generalities.Most of us garden in heavy black clay gumbo soils. We complain about how difficult it is to turn or rototill them. Curiously, the same organic matter that will help sandy soils hold moisture and nutrition will also help loosen tight clays. While adding sand to a clay soil really doesn't help very much or for very long, organic matter particles break up the clods of clay, leaving your soil more porous and easier to work with.Organic matter works its magic as it breaks down, and for that reason, it's always best to use a combination of several types of organic matter for the longest possible period of soil improvement.Many of us grew up using sphagnum peat moss, so that's a good starting point. After you do your first rough rototilling of the bare garden space, add 2 inches of peat moss, then 1 inch each of finely ground pine bark mulch, compost and well-rotted manure. With those 5 inches of organic matter, include 1 inch of expanded shale. It's a clay product that has been heated until it pops into porous granules, and it should take the place of any sand you might have added in past years. Texas A&M research has shown that expanded shale continues to help make clays better for 5 to 10 years, so while it's a bit pricey at the outset, its cost benefits will accrue.Retill the garden area to blend all 6 inches of those amendments down into the original 12 inches of topsoil. You'll end up with a planting mix that's almost equivalent to a professional grower's best potting soil. You'll get the sustained breakdown of the different types of organic matter, and that will give you the longest possible benefits. However, you'll want to add 2 or 3 inches of additional organic matter each time that you rework the garden for new plantings, whether that's two or three times a year or more.The question inevitably arises about which plants require this high level of "heroic" soil preparation. Certainly trees do not. Sure, they'd thrive in it, if you could meet all of their needs forever. But trees eventually have such massive root systems that amending soils for them is completely impractical. It's far more important that you choose a type of tree that's adapted to the soils native to your area. If you're unsure, check with a local independent retail nurseryman for the trees that best meet your needs.Similarly, there is no reason to amend soils as you're starting new turfgrass. If you choose a good type of grass, and if you care for it properly, it's going to be there for decades. Any organic matter you add now will be gone long before then. Fortunately, our common North Texas grass choices are all well suited to local soils. No call to action here.Shrubs are slightly more involved, and it all relates back to how large they will be at maturity. As with the shade trees, there's no point in counting on large shrubs that require major soil changes. That's why most nurserymen won't recommend acid-loving East Texas plants like cherry laurels and hybrid selections of American hollies (such as East Palatka) in our alkaline clay soils. However, as you begin choosing between medium-size and especially small-size shrub types, the value of good bed preparation increases significantly.And that brings us down to the smallest plants that you grow: ground covers, annuals, perennials and vegetables. All of these deserve the best soil you can provide, so it's in their planting beds that you'll want to invest the most in time, effort and soil amendments. It's entirely possible, for example, in a wide bed bordering your house, that you would have no additional soil amendments in the backs of the beds, where the taller plants were growing, and that you would have highly altered soils in the fronts. And if you'll rototill parallel to the bed edging, you'll be able to keep the areas separated as you work up the soil prior to planting.Drainage is the final concern as you get ready for planting. By the time you have added organic matter and expanded shale to the garden, you probably will have raised the grade by several inches. Of course, you'll want to keep weep holes in your brick wall open and unobstructed. Taper the bed down to the top of your edging, timbers or retaining stones, and the grade change will provide quick runoff of heavy rains.Bed preparation, including soil tests every couple of years, is best done in the winter, weeks ahead of the spring rush. Pick a warm afternoon, and get things ready to grow.Neil Sperry publishes "Gardens" magazine and hosts "Texas Gardening" from 8 to 11 a.m. Sundays on WBAP AM/FM. Reach him during those hours at 800-288-9227 or 214-787-1820.