Learning about secretarials comes with years of negative experience, IMO. You don't look at a ttm sig and an IP sig and straight out say they're fake.
In some cases, you don't learn what's fake until years later. Years ago, even big time collector's didn't know about a lot of the main secretarial users. It took decades for a majority to conclude Charlton Heston's ttms were fake.
The ones, like myself, who post about secretarials don't do it because it's fun to mess with someone (it's not!) but we do it because we don't want people doing what we did: wasting their postage, envelopes, time writing letters, photos etc...only to get a fake signature. Truly, there is no difference between a secretary signing and something that someone forged with Dick Van Dyke or Charlton Heston's name. One can use the "well, the secretary knows HIM" line but really, it's just an excuse (that people shouldn't feel the need to have) to make it less embarrassing to them. There's nothing to be embarrassed about. Many long time collector's gets secretarials, unknowingly. It comes with collecting, it's just a sad fact. But you need to move on from the fakes and focus on who does really sign, in order to get a great collection.

It's basically just comparing it to their in person signatures which isn't always accurate because most people sign differently in person and TTM because how fast they have to go.

I’ve seen a lot of comments where people will claim that a signature is a secretarial or say something like “She doesn’t sign. Only her secretary signs.” I’m curious where people get this information. I’m not saying anyone is right or wrong. I just want to know how you know this or how do you find out. I’ve never seen it on a celebrity’s web site and it seems like some pretty inside information.