A good start, would be to get away from where man dwells.
Here in Iowa most Red Fox, will den within a 1/4 mile of man. Coyotes a little farther away. Nothing is etched in stone [where] a critter will decide to make a den site. But, coyotes are more wary of man, so they will live farther away from man.
Places to look.
Most coyote den holes, I found. Where 3/8-1/2 mile away from any farmsted, acrege or active area. Coyotes prefer a view & prefer a place that has drainage. So they'll often den on a hillside, or terrace, whatever. Sometimes out in the open other times, hidden in briars, bushs or in a timber. BTW, they really like to hang around the timber.
A Red Fox or coyote den hole, under a hard structure/[building, boulder, log, ect]. Can be of any shape. Irregular, cup shaped, ect.
Canine den holes on soil;
Coyote [entrance holes], tend to be around 9-10"wide x 12-14" high. Point being, [most often the entrance hole, is taller than it is wide]. Most often, but not always. Red Fox den holes are slightly smaller in both demensions.
BTW, as for the chance to see young pups. Mid April-Mid May, are good months. Early morning & late evening are good hrs for viewing.
I don't recall any coyote or Red Fox den, not ever having atleast 1-exit hole. All tunnels will lead to a "den chamber" somewhere near the middle of where the tunnels intersect. Most often the eixt hole
are abit smaller than the entrance hole. Of both canines. You can often tell an entrance hole from an exit. As it will show the most wear/usage.
Sometimes, a person will find. Dead animal remains nearby the den holes. Sometimes not.
Here is an old abandoned Red Fox den.
Abandoned Red Fox den, used during Winter storms.