For home sites, the bottom line is pretty simple: You want soil that has good bearing capacity, exerts relatively low lateral pressure, and drains well, so that you can have a stable, dry foundation. The best natural soils for these purposes are sands and gravels. Silts and clays are fair, but the softest ones are poor. Then there are soils such as peat, expansive clay, and improperly deposited fill, which are so bad that they must usually be removed and replaced - often at considerable cost to you.
Power drills come in 3 sizes; 1/4, 3/8, and 1/2-in. Size refers to the largest capacity of bit that will fit in the drill’s chuck. 3/8-in. drills are the most versatile. They’re powerful, yet light enough to easily hold and manage. Larger bits can drill bigger holes, so 1/2-in. drills are best for big, heavy-duty projects. Drills with higher RPM ratings (1200-rpm or more) are better for boring smaller holes into wood. Lower speed models are better at making larger holes into metal.