I once taught an ex to shoot. She's now a better shot than I am :banghead:
That said, there's a certain mindset you need to have going into it. I'm teaching a friend to shoot at the moment, and here's what works for me.
1) Have a good long talk, preferably over lunch or something about the rules of safety and WHY they're important. Make sure they understand completely before even touching a gun.
2) Anticipate nervousness. When you show up to the range, they're going to cringe reflexively when they hear shots being fired. Give them time to relax and acclimate to it.
3) Show them how the gun works, but
do not fire it yet. This is important.
4) Once they understand the workings, go through safety again with the gun in your hand.
5) Fire one or two shots only. Do it quickly and don't go for accuracy. You're simply demonstrating stance and grip. There's no need to pull a 1" group at 20 yards. They'll only be intimidated by this.
You don't want them to compare their shooting to yours. This will only lead to frustration and disappointment. It's their day, not yours.
6) One or two shots at a time only, with plenty of breaks in between. Stress repeatedly that
accuracy is not important at this stage. They're simply learning how to operate it. Stand several steps away so they don't feel crowded. They shouldn't feel like they're being scrutinized or criticized. Use big targets, preferably something unmarked. At this point, they shouldn't be trying to hit the 10-ring, they should just be trying to hit the paper.
7) Admit it, you didn't do any better the first time you shot
Tell them this repeatedly. Give frequent praise for good trigger discipline and correct stance.
Nudge, don't push.
8) This should be fun. Don't discuss self-defense or stopping-power. Refrain from such words as "tactical" and "scenario."
As with teaching anything, you should point out that you're no different or more naturally gifted than they are. The only difference is time and practice. This is (hopefully) a lifelong hobby, not a one-day crash-course, and you're only guiding their first few steps into it.