Airguns are great practice and lots of rainy day basement fun. Crossman used to make an inexpensive set of steel silhouette targets that will last a lifetime, and are great practice.
They (airguns) have another very useful purpose. Getting people addicted to shooting. This is how I got my father-in-law hooked.
People who would never accept an invitation to spend an afternoon at the range with you will step down to the basement and give a "BB gun" a try, especially women. It's very non-threatening.
Here are a few hints:
Start with safety. Don't assume they know. Newbies will be more likely to relax and enjoy if they feel secure. Give 'em the same lecture (short form) you would for any firearm. Use eye protection. Make sure the newbie understands the controls of the gun, and how to make it safe.
Before the first shot is fired make sure they grasp the basics. Sight alignment, sight picture, trigger control. Don't overload them with a long lecture on natural point of aim, and breath control. They should be shooting from a rest, so just the basics will do.
Set 'em up for success. Let them sit, and give them a rifle/pistol rest. The objective is not to test strength, but to provide a positive experience. Have a variety of target sizes available. Start on a large "can't miss" target, and as they get better progress to the next size smaller. Don't skip a size. A feeling of progress is a powerful motivator.
Use reactive targets. Punching paper is great practice, but the significance of printing a small group is frequently lost on the newbie, whereas a target that falls over/down, spins or rings provides instant positive feedback. If you're shooting in a place where you can stand a little mess, try shooting Necco candy wafers. They are cheap and very reactive.
Be very complimentary and encouraging. Compliment a string of hits, even if it's just three. As the string of hits grows (remember start on a can't miss size) grow more excited. Your enthusiasm will be infectious. Stress their progress. Make at least a mental note of progress during this first session. For instance; if the newbie was hitting 4 out of ten times on the middle size target at the beginning of the session and was hitting 8 or 9 out of ten by the end, make a big deal of it.
Keep it light, it's OK to joke about how good the newbie is. Remember this is the "County Fair Shootin' Gallery" not the sniper duel of Stalingrad. Refrain from using terms like "number of kills". Lots of people who would love to plink would never hunt.
Quit early. Leave 'em wanting more. Quit at the first sign of fatigue. Finish on a positive note.
Invite the newbie to the range for a little 22lr action.
Have fun!