Procedures
Elsewhere, we have included "procedures" in our discussion. More specifically, procedures applicable to the operation of the aircraft (as opposed to airport or airspace procedures). Procedures for operation of the aircraft may come from several sources; the best of which will be the approved flight manual (POH) for the aircraft. It is sadly common that the flight manual is either not emphasized, or worse, not even available in the cockpit (it is required to be available to the pilot in flight by regulation). It's amazing what the manufacturer of a certified aircraft writes about it! They know a lot! They have both an interest, and a regulatory requirement, to provide the pilot with comprehensive operating information and limitations.
So, as the pilot, you should read the flight manual, really.... cover to cover. That is a really good use for poor weather days at the airport, 'plane is parked, the flight manual is not in use, and, there's probably someone around who can answer a question or two which you may have about what you read. Note that the "flight manual" for an aircraft, includes all of the applicable supplements too! So if the plane has been modified, or equipment added since it left the factory, there may be a flight manual supplement describing that system, and more to the point, there could be changed operating limitations, and you are responsible for being aware of, and flying within those. Included in the limitation section (2) of a modern flight manual (since mid '70's) will be a copy of every limitation placard - in case the one in the plane has fallen off. Example, there's me, left seat in a Piper Navajo (with little time on type), I've read the flight manual, and off I fly, unaware that an AD placard has fallen off, and I'm using full flaps where that plane is now limited to 25 flap - my mistake. If I'd read the AD'd FMS, I might have realized that a limitation placard was missing, and I should fly it differently!
Now eager organizations, and instructors (and even a few private owners) have poor weather days too. Sometimes they spend this time imagining, recounting, applying and writing "other" procedures. Okay, it's all in good faith, I get that, but what's the authority to require that the aircraft be operated that way? When we write flight manuals and FMS's, we follow specific formats, and carefully consider flow, and task saturation. We certainly consider not repeating the same action several times per flight stage! I've seen home made checklists, with the same item three times before takeoff!
So, read the flight manual (they're interesting, people like me, well including me....) write them. Then if you're presented with a procedure or checklist which deviates, educate yourself by asking how that alternate procedure is authoritative/approved. Now if you can see that it's identical to the flight manual checklist, except for the addition of a local procedure, like noise abatement or something, okay, that's wise. Or if it neatly combines a supplemental checklist into the basic checklist, without changing order, meaning, content or quantity, that's probably fine. But when you see a checklist or procedure which obviously deviates from the flight manual checklist or procedure [you have read, and recall at least somewhat], it's worth a discussion as to why that alternate should be considered more authoritative than the manufacturer's checklist or procedure. maybe you'll learn something, though more likely the instructor/club will learn that you bothered to read the flight manual, and recall the theme of it's contents. Note that Cessna, for example, is really good at providing procedures, and then "amplified procedures" in which there will be lots of wise narrative about why you should do it that way!
All that said, some things are basic airmanship, and should not need to be included in a checklist or procedure - like line up, before opening the throttle for takeoff! You're not off the hook for basic good airmanship because a checklist is not ten pages long!