I have read many times that the set back on a dirt hole should be about 9" or so. It happened again yesterday. We have about 4" of snow so I could see just what took place. Another coyote (this makes 6 in three weeks) dug out my dirt hole and put the dirt on the pan without touching the trap. I could see where its back feet were and again they dug out my hole because I was set bact to far IMO. About 10 years ago a good friend that trapped across the nation told me to jam the trap just like I would for a fox.

You can change the angle of your hole, too. Straight down, they have to move up a little to work it. Low angle moves em back a little. Two holes and they shift from one to other more over your trap bed.
I use my outstretched hand as my guide, pinky to thumb, from edge of attractors to edge of pan. Others have different methods. Find what works for you and your coyotes. Make some sets closer, some farther back. I don't believe there is a correct way in every situation. I set post sets farther back than I do dirtholes, for example. No real science to it was just what worked for me and what I'm confident in.
Jim

Put the trap where it put its feet. There is not a hard and fast rule for this. Like jabNE says. You'll get a feel for it.
You can put some guides in the dirt too. I like small sticks sticking out of the dirt where I don't want them to step like left and right of the spring levers.
Make your hole real deep - did you ever look at how long a coyotes front leg is- make it a couple inches longer than his front leg. Then he can't dig it out and he will have to step around more to get it out.
Another way is to slope your entry to your dirthole and put the trap on the slope in a trench going down into the hole.
The two hole set work great too. I make my two holes about 20'' apart and then i put the trap out about 12'' from each hole centered. Use a stake and make each hole about 1'' around and 10'' deep and put a different lure in each one.
hope these ideas help