First select a narrow spot in the trail or make a narrow spot. Bed your trap solidly in the trail. If an animal misses the pan and steps on some other part of the trap and it wiggles, that critter might either spook or start digging.
The critter you're after dictates the trap covering. If you're trapping coons a light grass or leaf covering will do. I emphasize "light" too much vegetation to top of a trap can let the critter slip out of the jaws. For canines, cover the trap with dirt and spread a little loose dirt on the trail. A canine can get spooky if there is just one little fresh dirt spot in the trail -- and/or camouflage the trap bed well. I use a stepping stick laid across the trap to guide the animal's foot into the trap. With a coilspring trap, the levers are set parallel to the trail and I lay the stepping stick just outside the lever. Use a stick about as big as your finger. You can put a stick on either side of the trap if you like. As for exclusion, you can keep out small animals by tightening the pan tension, beyond that there is little you can do.
Now with all this said, the reason you don't hear much about footholds in trails these days is that bodygrip traps and snares tend to function better. However, in Ohio the largest bodygrip you can set on land is a 5X5. You can, however, use a snare.
Also, check your trails carefully. There are a whole lot of deer in Ohio, and they make a whole lot of trails. It's hard to keep a trap working in a deer trail.
Endeavor to persevere.