You would have better luck going out early in the morning. Before the heat of the day (for finding stuff, and for taking better pictures). Going out at night might seem more logical, as that is when the snake's are often most active, but when they are active you're really less likely to bump into them. Plus, in the middle of the night you don't want to be stumbling around in the dark with only a flashlight. Mainly because it is hard to see where you're going and where you're putting your hands, but also because there are potentially dangerous species (copperheads and rattlesnakes), and other things like scorpions in areas snakes like to spend time.
Not to mention, during the day you will also have better luck finding lizards, which are always photogenic.
Find some old farmsteads, places with lots of debris and trash on the ground. I'm not sure how much it is used in KY/TN but sheets of roofing tin are used for farm buildings here in Texas, and often sheets of it are laying around the ground. They are like a magnet for snakes, as they warm up during the day, but yet still afford them the secure cover they prefer by huddling underneath it. Pieces of plywood, old tires, heck, I even found a 30 inch long prairie king snake huddled under an old t-shirt once. It is amazing how small of a space they can fit into.
If you do want to go out at night, find some dark farm roads off of the main roads, and drive slowly down them. Especially a road near a pond/lake/creek. Quite often you can find snakes and amphibians crossing the road, or sitting on the edges of it warming their bodies on the asphalt because it holds heat from the day. Just don't shine your flashlight from the car, that's illegal, and make sure when you see something to pull as far off the road as you can. Sticking to the road is a little safer than tromping through the brush, but sometimes you have to move pretty fast to catch something before it makes its way off the side of the road.
You may want to double check with your state Fish & Game, in many states a hunting license is required to do such things. Even if you're just releasing them after you get a picture.
Most snakes in the US breed in the spring, eggs are laid and hatch out in the mid-late summer. Gives them time to fatten up before winter. A few species breed in the fall, overwinter gravid, and give birth the next spring. About now is when one should start finding this year's babies, especially since many areas had such an early spring. If you Google for a specific species, I'm sure you can find all the info you want on them. North American species are quite well studied.
