If you are hunting elk in a team of two people with one attempting to call it in and the other to kill it, where should the caller be in relation to the hunter?
The caller should be at least 50 yards downwind of of the hunter. The reason is that elk have a good sense where a call is coming from and won't get very close (usually around 50 yards) to that spot unless they see another elk. If the caller is right next to the hunter, the elk will usually stay just out of range.
However, if the caller is back more than 50 yards, then the elk will come much closer to the hunter.
You need to optimize for putting the shooter in the best place to intercept the bull on the way to caller, while keeping both the caller and shooter downwind of the approach. The bull will try to approach the caller from as downwind as possible, depending on how angry/horny he is.
Generally, you will have an idea of which direction the elk will come from and what the possible approaches are. The elk will get close to where he thinks he should be able to see the cow or bull that is making the noise (the caller), and look around, also called "hanging up". If you can figure out where that will be, you set the hunter up in a spot with a good view of the ambush site with enough cover to draw behind as the elk approaches. Hopefully the elk will approach right into the ambush site and sit still while he looks around giving a good shot opportunity. Thickness of the terrain and certainty of where the elk will come from will determine how confidently you can place the hunter in the right location. Sometimes the terrain makes one approach a near certainty and other times it is difficult to tell.
When you aren't certain, the hunter needs to be closer to the caller because you are less likely to be in the right spot when the elk steps out. If the elk gets around the hunter to the caller, it is unlikely to work out.
So the summary is that the hunter should be as far in front of the caller as possible while still being relatively sure the elk can't slip around behind and end up sniffing out the caller without the hunter having a shot. Terrain and wind will dictate all for each situation.
(And then, once you have it all figured out, a little spike elk will come down and impossible cliff face to bust you right as the herd bull is about to walk into your shooting lane.)