Recording acoustic to me is a balancing act between having a nice sizzly top end, but also having enough bottom to not make it sound harsh. But too much bottom, or too close to the soundhole = muddy jumpy lows and low mids. For some reason, it helps me a lot to imagine a high and low shelving filter in action while aiming the mic.
And I agree aiming for the 12th fret and then turning a bit to the neck or soundhole depending on what you need is a great starting point. Don't be afraid to move the mic a bit further away from the guitar too. Especially if you have a nice room.
Another position I have liked is with the microphone over the strumming-arm-shoulder of the player. Gives you a sound similar to what you hear yourself while playing.
But most importantly: try every point of the room to find out where the guitar sounds best! This can make the difference between a mediocre recording and a great one imo.