Can someone describe the process of getting TSA Precheck-in detail? Is this just an electronic application? What is the interview? Are they doing these remotely? Where? Cost? Can my wife and I arrange to go together to the interview? How long does the interview take? How long to be approved? Can we just do this at the airport while on our way to a trip (i.e. knock this out in 10' with instant approval)?
You can definitely do it at the airport when you are planning to travel, but in no way should you expect "knock this out in 10' with instant approval". You won't get it on the outbound flight.
However, if the nearest office that takes the application is at an airport that is far from you, then yes, it's possible to get to the airport early to do the processing, and depending on how long you will be gone and how backed up the agency is, you might get your Trusted Traveler number via email before your return flight. (In which case you need to log into your FF account and add it before your check in for the return flight, because it MUST be printed on your boarding pass or you will not be allowed to use the precheck lanes.)
To start with, you fill out a form online to determine if you are generally eligible. Once that is done, it will invite you to make an appointment for the in-person part. The actual in-person processing itself for Pre-Check takes about 10-15 minutes, though if the office is busy you may have to wait to be seen. (In my DD's case, I took her to a local non-airport contract office, and even though we had an appointment, we had to wait for about 45" for the only clerk authorized to process them, because he had been sent elsewhere on an errand.)
As to how it goes, IME, you are taken to a private office where your information cannot be overheard by people in the waiting room. You are asked to walk the tech through filling out your basic address information, DOB, SSN, etc., then they will scan your ID documents and take your fingerprints, then process the fee payment. At the airport offices that DH, DS & I went to, they took walk-ins, but anyone with an on-time appointment got to jump the walk-in line.
There are many office locations other than major airports where they accept applications; you can do a search by zipcode here:
https://universalenroll.dhs.gov/programs/precheck
The cost is $85/pp, good for 5 years, and most people pay by Credit card, though I'm sure they take other payment methods. (Some credit cards will rebate the fee; my CapOne Venture card rebated it for everyone in my home.)
