RE: What do you do when?
This is what I would do. I would try to get your buddy as comfortable in the woods as possible. I've started a couple of my friends out sitting practically back-to-back nearby. My friends were nervous, figity, and noisy (coughing, snorting, etc), but I was bringing them into a sport that I loved. It was new to them. But as they got more confident, they went their own way, found their own successes and failures. You might not want to take them to your "honey hole" to do this as they will probably try to return there. You may have to find a totally new area to hunt with them.
I remember hunting back-to-back with my dad (even before I carried a gun). My dad taught me patience, woodsmanship, and sportsmanship. To me hunting was and is experienced best when shared. That's why we are here right now, sharing our trials, tribulations, successes etc.
If they get a deer and you don't won't the trip still be rewarding? You can share in their sucess. Familiarity will bring confidence that they can do it on their own.
Passing on the tradition and heritage is what will keep this sport alive.