I've mostly used a mouth-squaller to call them in, imitating a wounded rabbit.
Coyotes will come toward the call, but they tend to circle for a final approach into the wind. That means you have to pick a position which controls that final approach, whether land form or thick brush. Try to force Wily's approach so he comes in cross wind or directly to the call.
You don't need camo, but setting up where you are behind low cover is good. A little face-net mask hides the shine of your face. The main thing is to not betray your presence with motion; don't fidget. Whatever motion you make, do it slowly and smoothly.
There is all manner of electronic calling gear available. I guess the top of the line is one with a remote control like a TV, where you can sit at a distance and control the volume. But I have on occasion used a "baby boom box" from Wal-Mart and just set it on the hood of my truck. It worked...
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