For about 6+ months now, this has been one of my favorite training things.
You can click whatever you want, and theoretically all goes well. But how and where you deliver the reinforcer can greatly add or detract from a training session. This can impact the shape of the behavior, the speed of acquisition, and the speed of deterioration of the behavior.
At training group today, I worked Griffin on several different exercises:
1) Dumbbell retrieve. I was specifically reinforcing a straight front. I would always feed the treats centered with my body and from my center line. It would be best if I could magic them there...but couldn't happen.
2) We did two sessions of Drop on Recall. After the click, I would send my dog to a Trained Treat Feeder behind him. The person would feed him treats until I arrived ("Race to reward" technique from _Agility Right From the Start_).
3) Scent Work: We did 2-3 sessions. After he indicated (down, nose to the odor), I would click and then feed the treats so that his nose was further pointing at the reinforcer.
I could have reinforced in other ways. Variety is a key part to training. That said... I do make an effort to feed in a way that will enhance the behavior and NOT detract from it.