If I wanted to take a friend climbing, and this friend is familiar with ropes and knots, but has never used a climbing system that tree climbers use, and has never climbed a tree, how would you set them up for their first ascent. What gear would you give them, what knots, and most importantly, which things would you purposely leave behind?
If they're going with you, I'd basically treat them as if they were a beginner at one of our intro climbs. You should set the rope, tie the knots and give a demonstration. Then set them loose. That's how I always introduce friends to the sport. After they get hooked, then I show them more. But start as if they're someone who's come to an intro climb.