In my opinion if you are hunting public grounds, like in Nevada where you can hunt 80% of the state, you would use the locator the night before your hunt to pinpoint the current location of the family unit.
As for my hunting grounds, smaller properties here and there, I hunt when and where I can. I have tried the locating howl the night before a morning hunt and have got no response when I knew coyotes were there and I have gotten a response and called nothing in the next day!
During the breeding season, now for my area, I will use more coyote vocals or howls. But I keep them high pitched to imitate a younger coyote so that I might not intimidate the locals.
Most of my howls are more like the female invitation howl or a young interrogation howl.
Coyote vocals are difficult to translate, for me anyway! I would watch as many videos of actual coyote howls as you can find as reference.
However you can always speak to their belly!