Well, this time of year is prime mating season so a good lone female howl should work well. If you don't have any action after awhile then you can mix in a male howl after your female howl and another challenge call after that. Pup yelps and the sounds of a wounded or fighting 'yotes can also be used. In many ways, it is like fishing in my opinion you keep throwing something at them hoping they "bite".
If you aren't howling, in my opinion you are missing out on a lot of song dogs. I use to rely too heavily on distress calls with lots and lots of empty sits. After sitting down and talking with a guy the biggest point he made with me especially in the midwest or any area with abundant food is distress calls don't work when the coyotes don't have to move much to find food. With loads of deer, rodents, turkeys, upland birds (very few), and rabbits- coyotes aren't always hurting for their next meal or "urgent" to run to a distress call.
