First, not everyone with desire has mechanical
aptitude. In a volunteer group, usually the organizer generally won't have the ability to pre-screen some out. Sometimes the only thing that can be done is to keep reemphasizing the need to ask for assistance.
This isn't what we do at Velocity, but here are my thoughts (I've keep going back and adding in thoughts, so it is now a bit disjointed, sorry):
If basic maintenance classes are offered on a routine basis, have the volunteer audit the class at least twice. Have them bring their own bike and if a stand is free they can work on it. I believe these are the basics a volunteer needs to be familiar with so they have a common starting place, understand the most common things they will see in the shop nd know both their own limitations (I sure have them and tell my students so). It's also a basis for rehabing a bike for resale. If no class is offered, then this is my list of what I like to work on teaching new volunteers. Till they have audited the two classes and rehabed a bike as a demonstration, their other time in the shop is watch and learn, ask questions, or tearing down bikes that can't be rehabed. Tearing down bikes can always be set aside for a learning opportunity.
In the classes I teach, I cover:
Overview of the syllabus. Basic bike layout, "righty-tighty," except for two places we won't be touching, tool use and care. Quickly as they have a hand-out for later reference.
Air: Inspect tire. Dismount front wheel, remove tire, and tube, inspect, reassemble and remount. Dismount and remount rear wheel. Patch a shop tube. All hands on
B: Brakes. Inspection and adjustments. Hands on adjustment of own front brake. Show and tell minor wheel truing for proper brake adjustment.
C: Cables & Chain: Clean, inspect & lubricate. Show and tell on one bike (explain you will cover derailleurs at the end)
D: Derailleurs, shifters, and chain ring, sprockets, cogs, etc. Show and tell. Have students observer their own pulley/jockey wheel/gear alignment and what the limiting screws do (and don't do). Show or discuss friction shifters to help explain derailleur tuning. Show how to relieve derailleur cable tension while explaining how a derailleur works. Cleaning, and lubricating. Using Simple-Green to save $ followed by Clean-streak or similar.
ABCD is easy to remember. Not original to me, but I think it works well. Based on this I can also leave a quick note on a rehab bike that didn't get completed noting what work has been done/needs to be completed.
With hands on what I think everyone needs to know through hands-on to stay safe and "Show and tell" of the rest, I can cover the syllabus in a little under 3 hours. Classes are usually from 6:30 - 9:30 every other Tue. Four different bikes with four different brake types will consume the most time. Some students will be bored as they won't care about other types, I just accept that and try to keep them engaged.
I teach brakes are the most important followed by tires and no loose fasteners. These are the things that can kill a rider.
For the things I do "Show and tell" I encourage students to come back to the shop for help on their first try. I teach them about using a book and the internet to learn. And to ASK QUESTIONS. I have students read aloud the instructions inside the Park patch kit and offer why it is important to follow the directions. We get a few laughs and I tell them we all pay for some of our lessons, but I'm trying to help them not pay for the ones I've already paid for. Usually at least one student doesn't fully hear or understand, and we talk about asking questions. And how hands on after hearing helps things "click."
We're fortunate and my employer supports my volunteering with reproduction support so I give them a copy of my 30+ page syllabus that has a maintenance list/schedule, some web links and a book list. I just added a basic trail took kit list; tube & patches, multi-tool and leavers, & pump. It's always a work in progress.
So back to the new volunteer:
If a new volunteer can do all of the above work, IMHO they can assist patrons with 90% of what will come in the shop. And not set anyone up to kill themselves. It will take a while to cover the different brake types, but if they can do a Vee brake, then they will see what is most common right now.
If a new volunteer is starting from absolute zero, start them off stripping bikes. Always have some set aside for them to work on so they won't be bored. They will be in the shop where they can listen, observe, and learn. And ask questions.
100% of new volunteer work is inspected for at least 6 months. Just another pair of eyes, AND it gives the new volunteer opportunities to learn from someone with more experience on what they may have missed. And learn vocabulary as they explain what work was done.
This seems like a good topic to have on the wiki, would like it structured so there are multiple options listed, not just one article.
IMHO,
Ron