On appointment day you should expect the piano tuner to arrive on time. If you are the first appointment of the day, your technician may arrive at the exact moment agreed upon. I start at either 9 am or 9:30 am. I can honestly say that I'm never off by more than 10 minutes, usually due to unexpected traffic. The other appointments are trickier to be that accurate. Unforeseen repairs or tuning conditions can make the previous appointment run longer. I like to space my tunings out by 2.5 hours when the customers live in the same town. Again, I'm rarely late, but if it's going to happen, I always call to let my customers know that it's going to happen.
When the tuner arrives, he or she should be cheerful. This is because we love our job! I can't think of a single time when I arrived and I didn't want to be there to help a customer with their piano.
You may ask them to remove their shoes, and I expect all tuners in the city to be ready to do so. The occasions that I like to have my shoes on are when I'm tuning an upright piano over a new hardwood floor. The floor is too slippery under my bare socks, and a secure posture is important to technique. My mother lives in Vermont, and there is a sort of culture and expectation of a little dirt around the house, so I can appreciate that the "shoe rule" doesn't apply to all geographical regions.
The first thing you, as the piano owner, should prepare for is the technician to open the piano, so you should remove anything from the top before they get there. Usually the lid of the piano is home to music books, pencils, children's toys, pictures in frames, sculptures, lamps, etc. If you don't remove this stuff, the tuner will have to do it, and their fear is that something will get damaged. Even when I arrive and there are things on the piano, I kindly ask that they remove everything because I won't know where to put it.
The tech will need to take the front panel off to get access to the strings, action, and tuning pins. This should be done with care by the technician. If he or she doesn't seem to know how to get the parts off, give them a minute. All pianos were created differently, and sometimes it's not obvious how to remove the parts. But if it takes more than 5 full minutes, this might be a red flag that they are green, or just don't have the proper training.
Piano tuning takes an incredible amount of concentration. A tuner listens to the relationship of two strings played together and adjusts one string, listening for a very small variation in frequency. It's expected that there is near silence while they are doing their work. Loud conversations, television, and vacuuming is not recommended. Sometimes people like to have the plumber, HVAC tech, cleaning crews and the piano tuner all scheduled on the same day since they may have to be home from work to let everyone in. Resist this urge!! I can't tune properly while there is so much auditory interference.
The worst thing you can do while a technician is tuning your piano is wash the dishes. The sounds of a faucet and sharp clanging of porcelain, glass and metal are infinitely distracting. It's possible to tune a piano while these things are happening, but don't expect to record your hit single afterwards.
The appointment carries on though, and around 1.5 hours later they should be done. I usually play a few chords of songs that I would like to master, and that's the cue that the tuning is finished. The piano get's closed up and I briefly discuss when to expect to tune the piano again. As I've said before, your ear is the best judge as to when you should make an appointment.
Thanks are exchanged, as well as a polite handshake, and the fee for the work performed. I expect that services are paid for at the end of the visit in the form of a check or cash. Some tuners use a credit card service on their smart phone like square reader, although I'm not sure how well that has caught on yet. I don't like to carry receipts, but prefer to email a copy to the customer if it is requested. Ask for their business card, and if you're happy with their work, refer them to a friend, music teacher, or on a website!