This question comes up with some regularity, so this is an (albeit incomplete) compilation of posts that have been written on this topic. I hope others will add more and that it will be useful to piano owners.
First off, there are professional organizations that have considerable memberships spread across all of the USA and Canada. You can search for members on their web sites.
Piano Technicians Guild: http://www.ptg.org/
Master Piano Technicians: http://www.masterpianotechnicians.org/
Further, if you are in Canada, check out: http://www.capianotechs.ca/index.htm
Here are a few quotes lifted from different threads:
"Most techs that are Registered Piano Technicians (RPTs) with the PTG are good. The fact that they went thru the RPT testing indicate that they are serious about the quality of their work. Certainly just finding an RPT isn't a guarantee of high-quality work, but it is a strong indicant."
" 1. Talk to fellow piano owners. Ask for recommendations. When you call to schedule a potential appointment, make them take a few moments to tell a little about themselves regarding their experience and training. You will find that most piano techs simply love to talk about themselves and how great their skills are.
During this brief portion of the conversation try to get a feel for the way they feel about their job, their philosophy on customer relations, etc.
2. Find someone who cares as much about your piano as you do. Disregard "talk"; look for demonstration. Do they not just tune a piano, but do they know the piano as an instrument as well as they do their own "glorified" body, to the point they can competently do major and minor repairs. Ask some "dumb" piano questions, knowing the answer and evaluate their response.
3. But in the final analysis, you will need to give a tech a paid "trial" run. If you dont like what he or she does, move on in your search.
4. Lastly, and this is sure to raise a howl here in the forums. Fine yourself a good aural tuner. I have tuned for almost 25 years and have yet to hear an ETD tuning that really makes the grade. Frank (the owner and manager of The Piano Forum)give me the boot if you must, but I am so sick and tired of following ETD tuners who take people's hard earned money, for a piano tuning that is in most instances, second rate at best!!! "
"Contact the nearest institutions to you that own concert pianos and ask them who takes care of their instruments. Unless they bring techs in from somewhere else I'm guessing that whoever works on the concert pianos also does a lot of work in private homes."
"Along with the universities, check local churches that have a vibrant music program. Just a few minutes talking with the music director should give an idea of how they take care of the piano!"
"If you've got a local symphony call the center and find out who they use. Or call your nearest college's music school and see who tunes all their pianos. "
"I've run through four technicians in the last three and a half years and I still haven't found the right one. Sometimes, I think getting married was easier! Having exhausted all the obvious sources of information, I've concluded that the best approach at this point is to try to get recommendations from people who've actually had good experiences with technicians in this part of the world working on pianos comparable to mine."
"A personal recommendation from a skilled pianist that owns a fine piano is a great way to go.
The geographic repositioning of your piano will give you ample time to find a good technician. The time necessary to complete it's acclimation could take 2 years.
In the meantime, plan on tuning the piano regularly to keep up the pitch. You may consider humidity control as well.
Even a cheap, inexperienced tuner could help you to keep the piano to pitch in the interim. When the piano is stable and you are ready for the fine tuning and regulation, you can also get a recommendation from a music conservatory, or a dealer that sells highest quality concert pianos. Ask for the concert tuner ... their A+ technician."
"Using the "Search" link at the top of the page, you can search for threads on any topic by specifying key words. By doing this you can get a lot of information quickly and spare us from reiterating everything.
A quick search for "finding technician" or "Find tech" lists over 300 threads. Refining the search gives a smaller group of more narrowly focussed threads. Below is a tiny selection which gives some answers to your two questions: How to find a good tech and what questions to ask. Very many new piano owners have these same questions (they all should), and no matter where in the country the piano may be, it doesn't really affect how to go about finding a tech."
Interview your prospective technician. This post outlines some of the information you can ask about:
"I get a certain number of calls that start (and potentially end) like this: "How much does it cost to get a piano tuned?"
I realize the client is going through the yellow pages, looking for the best "deal".
I proceed to tell him or her about my training, my experience, how I tune (aurally) and who/what I tune for (teachers, musicians, concerts, festivals etc). I also tell them that there are tuners who cannot do repairs and service work properly.
I encourage them to go on looking if they feel so inclined, and I tell them to ask the questions that I just answered. I also make them aware that $10 in percieved savings can actually be $100 in wasted money.
If you think about it, there is no way you can expect the best service in the low end of the cost scale. This applies to almost every service"