In general, you should follow the directions included with the plant you buy. Dig a hole to the proper depth as instructed. You will also want to control the soil's pH (acidity). Add lime to increase pH, or add manure to decrease it. Make sure these are well mixed with the soil though, because concentrated clumps can damage your plants. You can buy pH measuring kits and test the soil yourself. The soil should be well tilled and loose.
When you dig a hole to plant in, do not feel compelled to refill that hole with the same soil you removed from it. For the ambitious, there are dozens of soil recipes to choose from, combining loam, vermiculite, peat, lime, fertilizer, sand, compost, charcoal, manure, etc. You usually only need a gallon or so of soil per plant, not 40 acres of perfect dirt.
