I use a shovel. (-; If your ground is mostly clay, you may need or want to amend it with compost or some other organic material, or use raised beds. If the ground is rocky, you may have to use raised beds.

So far as what plants to use, there are an infinite variety. Are there specifics about what you are looking for? If you're looking for something that is drought resistant, you could probably find numerous recommendations by googling something like "xeriscape Tennessee".

I hope this answers your questions to some degree. If you have more specific questions, just ask.

Can't help with plant selection, but I know what you mean about the clay. I have one side of the house that is just undiggable. I have started adding grass clipings and coffee grounds to the area I want a bed in. After a few weeks, I can get the shovel in the dirt a couple of inches. So I am going to just keep adding and turning until I get something usable in that area.

I'd also make sure it's at least a little bit damp otherwise you'd have more luck digging in cement. As to your second question it would depend on the look you're going for . If you like tropicals try crepe myrtle, magnolia, sable minor, sable brimingham, needle palms or hardy bananas. Anything you plant here that's not a desert plant will probably require some water in the dog days. We tend to have a couple of month period most years where we don't get a lot of rain.

Use a Mantis tiller as it makes short work of our rocky red clay here in Northern Virginia. It is also great for mixing in soil amendments.