I think that most of us make the mistake of calling areas that we have already exposed ourselves to, either by sight or scent. And calling to a coyote that you see standing out in the open is pretty much just educating the critter.
It's usually kind of frustrating to me trying to figure the exact best spot to plop my butt down and start calling; too much visibility and they will see you first. to little visibility, and they'll often smell ya first. And then of course if there's no coyote within hearing distance of your call---- well ya know. When you stack it all up, the odds of being successful on any given stand are less than great.
jd