use the wind to your advantage. have the wind in your face. complete camo from head to toe. be still. the smarter coyotes will try to wind you so try to sit with something at your back so they can't get around you, water or anything else that will deter them from winding you.
If you can't find a barrier that prevents them from getting to your downwind side, then set up with the wind from your back side, while you're facing the large open fields. Most coyotes want to smell the source of the sound, so most times they will try to get downwind, so force them to come out into the open fields to smell you. Sometimes they will stay in cover, and come without trying to smell the source, if so, then at least they will be close enough in heavy cover for you to see them.