I don't have much experience of this but was given to believe that stags would come running to the call without care or caution and I've not found this to be the case.
I called two big stags last year, there has been no real rutting activity this year so no chance to try it yet, and they both came in very cautiously to about 150ish yards before beating a retreat. Neither replied to my call. I got the impression that they generally like to get your wind rather than just come straight in and one of them did vanish into cover and work his way around me until I heard him running off in the cover. So you need to keep your eyes open and be aware that the stag might stand off by 150 yards or more. Also one of the stags I called in, to my amazement, crept up a ditch so I could only see the top of his antlers and then jumped from the ditch into a group of trees and watched me from the cover of the trees. Had I not of spotted the tips of his antlers while he was in the ditch I might never have known he was there.
There was an interesting item in "Sporting Rifle" (yeah, but I was on holidays and needed something to read on the ferry) about calling foxes and the chap suggested that foxes like to get the wind of the thing they are hearing. He was making the point that if you are in a high seat or similar then it is better if your scent is blowing out onto the open ground rather than the other way around. His reasoning, and I suspect the same will work with sika stags, is that the fox will cross the open ground to get your wind giving you a shot whereas if the wind is blowing into cover then you will never see the fox. My very limited experience would tend to support this approach and both of the big stags I called in last year worked in that way to some extent.
So my tip is to watch for a very cautious approach and to be aware that an approaching stag may well try to get your wind rather than coming directly in to take a look. When it works it can seem like magic but don't expect it to be as simple as blowing the call and then shooting the hundreds of stags that come running.