This is a question that appears to be so basic, you have to wonder.
But, taking it seriously, is there anyone that hasn't stepped in one of those land mines out in the yard? Gooey pile, usually some shade of brown, uniform consistancy, definitely no hair, and almost guarenteed not to have bone splinters. This would indicate a pet animal, of some sort, even if he is romping in the woods for an afternoon.
I can usually spot coyote scat at thirty miles per hour. Depending on age, it can be green, olive drab, or gray or black with a deep chocolate tinge. Texture is diagnostic. there will be chunks and hair, beyond doubt. Also, look for a glaze. Older scat left todry in the sun will be light gray, but it still will retain the basic shape, frequently with segments, by the way. Another thing, coyotes do prefer to crap on a road, so that is a subliminal clue not to be discounted. Left on a rock, maybe a little smaller, probably a fox?
Depending on the time of year, coyote scat will have green vegetation. In my areas, that would include grapes and mesquite beans, and melons, in season. Don't expect to see hair or other normal clues, the effect seems to be similiar to a laxative; usually green and slimey.
Subject not addressed is feral dog. Have not observed this behavior, so I can't say for sure. My guess is that it is distinct from coyote, but not like domestic, either. In either case, it is not particularly important that we be able to ID every one of these things. I just like to keep a mental note as I drive through an area. That's another subject.
Good hunting. LB