For general cleaning:
On a poly finish, a mild soap such as a few drops of Dr. Bronner’s Pure Castille soap in water on a rag wrung dry will remove most offending oils (such as from your arm, cheek, chin, hands, etc.).
The same is true for a relatively young NCL (lacquer) finish. But water is not a friend of wooden instruments, so if finish cracks exist, let alone gaping cracks in binding or open wounds exposing raw wood, then soap and water is *not* advisable. Your only choice is Naptha.
Naptha is a relatively safe all around cleaner, but it is *not* a good choice for maintaining fretboards (Naptha , a mild solvent, has a “drying” effect on wood over time). Fretboards are rarely, if ever finished. They are raw wood that (typically) have been oiled. A very light application of mineral oil works as both a cleaner and a prophylactic on most fretboards.
Do not use alcohol in any form, as it may/will cloud your judgement; er, finish.
With any liquid, be cautious of wiping smudge, grime, grease, lipstick, body slough off, etc. down into cracks and crevices. You won’t likely ever be able to remove stuff once you have smeared it in to those places.
For “sticky” finish:
Controversial topic. I am deeply aware of two opposing views regarding sticky finishes: 1.) They cannot be fixed, and must be replaced. 2.) They *may* be able to be fixed if they are localized (eg, back of the neck between the 1st and 3rd frets ONLY). How to do it is a secret.
Just kidding. It is not a secret, but it can be risky, and you end up needing aeither a spot refinish or a complete refinish.
Word of advice: Test your mild cleaner of choice on as inconspicuous an area as possible before wiping it all over your instrument, just to be safe.
(Second) Word of advice: Go slow and watch for issues.
