A question I'm frequently asked is "How do I select a good acting coach or teacher?" Of course, the easy answer is "Choose me!" Naturally, I'm a bit biased on this one, as I teach acting and directing actors at the Academy of Art College in San Francisco, as well as my own studio in Rancho Cordova. I also work as a dialogue/acting coach for movies and television, most recently for the BBC in London. However, I can tell you what I personally look for in a coach or teacher. (Yes, after more than forty years, I'm still studying my craft, as do most professionals.)
The first question I ask is, "Does this person work professionally in "the business?" If they claim to be a professional actor, do they belong to any of the actors unions? If they are really a professional, they will belong to the Screen Actor's Guild (SAG), the American Federation of Television and Radio Artists (AFTRA), and/or Actors Equity Association (AEA). Although it is possible to get paid for some local work, all true professionals will belong to one or more of these organizations. This doesn't mean that every working actor can be a good teacher, or that there aren't some good teachers who haven't worked as an actor, but it's a good place to start. There are people in the area who claim to train professionals, but who have never worked professionally. They may have taken some classes from those who have worked, so they can say they "studied with so-and-so." They may even be able to pass some of what they learned along, but that's still not the same as working as a professional actor.
There are some pretty good classes offered by good teachers at the local colleges, but keep in mind there is a real difference between the academic world and the "real world" of acting. (Now there's an oxymoron for you!) Everyone should get a college degree if they can, but sadly, one can attend a fine college, get a Master of Fine Arts in Theater and in many cases have absolutely no idea how to go to work in the business. That doesn't mean the classes aren't valuable, just that what they tend to do is to prepare you to become a high school drama teacher, not a professional actor. That being said, Go Get a Degree! You'll be glad you did.
Beware of the big "chains" that offer modeling and acting lessons. There is one in particular (no, I won't mention the name 'coz I don't want to get sued! I really don't know how they stay in business, as they have dozens of complaints against them with consumers' groups such as the BBB) that offers acting lessons, pictures, etc. . One of their former instructors attended one of my classes, and told me he had taken a class from them - it cost more than $2000 - and although he had no other experience as an actor or teacher, they asked him to teach the next class. Fortunately, he refused.
In summing up, ask to see the resume of any potential teacher or coach. Where have they worked professionally? Do they belong or have they ever belonged to any of the performer's unions? What teaching experience do they have? What do they charge? Most charge around $300 for a once-a-week, three hour class, and around $40 - $50 per hour for private coaching. What size are the classes? You want to be sure that you'll get to work almost every class.
So learn your craft. Study with good professional teachers. No one teacher (including me) has "It," so take what you can from each instructor, make it your own, and apply it to your craft. Continue to grow and learn, and remember, you really learn to act by acting! You should always be in a class or in a production. Besides, it's fun!!