Even in the best productions, I've seen good actors fail on both counts. It can be hard to watch, but it's also part of what makes each live theater experience a unique event. A few years back, one of the city's best professional actresses wrote an op-ed piece, the gist of which was that those without formal training shouldn't even be on the stage. My response would be that people with that attitude should dismount their high horses and find some new blood for the local theater scene. I would also contend that community theater is the backbone of all live theater.
Small companies are also a superb training ground for amateur actors of any age.
So take Spencer Tracy's advice. Here are a few tips on how to start. Over time, Stewart says, you'll get to know the people associated with the theater company, including directors. Sweat equity pays off. Study the craft.