I had been recording myself and various bands on a rinky dink level for around 8 years before this happened...
The dearly departed forum member Loudist / Steve Gursky asked me to mic up a guitar on a session, I think just to F with me a bit.
After watching me do whatever crap I did, he broke out a lighter, found the center cap of the speaker through the grill cloth, jammed the mic so that it was touching the grill and then sort of "bounced" off of the grill a bit, maybe a millimeter away.
His explanation on this to me at the time (best as I can remember), was that it was closest to getting a direct injection of the guitar amp. It was the LOUDEST position (hahah), which would sound most present, not have an unreasonable amount of bass (like the edges of the speaker) or an ambient quality that might not be needed. It is the most up front, popping out to the front of the mix sound you can get, and if you don't capture it, it is quite possible to regret it later on.
We were in fact aiming for an upfront tone, and there was listening involved in the final adjustments, especially as far as the mic choice itself went. I don't want to convey that it was only by sight.
He advocated strongly for "sound reinforcement"/live sound approaches as the starting point for the recording studio, to some degree, and to get fancier when that isn't working, or for creative purpose.
I have really come to appreciate how well that mic approach can work in a mix and how useful it can be, even if it may seem jarringly close if you don't typically mic from that position.
On another note, he also showed me about putting a mic directly on the floor, to get that sound that happens when you literally have your ear by the floor... usually for lead type parts where you really DO want to hear the room. Or aiming it at a nearby wall, very very close to the wall, like a boundary mic basically.
To this day, I sort of view those as the extremes, and then there is everything in between.
Another point - try out the guitar with whatever you consider your "best mic". Why not? It's a good idea to try them all out, so that you know how each mic will tilt the tone, even if you wind up having one "go-to" mic.