i like new strings
i've got
a martin d-15 (all mahogany) and i use the martin SP phosphor bronze strings (lights) on it. they sound better on that guitar than the martin sp 80/20's do, and they last a little longer, too. the 80/20's were a little too "brassy" sounding. the phosphors are more warm/smooth to go with the mellower sounding all-mahogany guitar. the PB's have also helped minimize finger noise.
i record it with 2 mxl603's. i put one about 8-12 inches in front of the guitar, aimed around the 12th or 14th fret, depending on whichever sounds best. i've found that a tiny bit of movement on this mic can intensify or minimize finger noise, so fiddle some and see what works best.
the other 603 goes over my shoulder (next to my head), pointing straight down at the floor (aiming over the lower bout of the guitar). this mic is about even with my ear and more or less captures what i'm hearing while i play. it also gets a solid amount of boom/bass without it being overly so. sometimes i aim the mic a little back towards the guitar, and sometimes i aim it almost perpendicular with the floor.
sometimes for kicks and grins i'll throw my B1 out about 4ft from the guitar, also aimed more towards the neck of the guitar than the soundhole. the B1 will pick up an inordinate amount of undesired boom if you're not careful about it.
but the absolute best thing you can do when recording acoustic guitar is to put new strings on the day before and let them settle in a little. play on em for an hour or so and break em in. that way you don't get that harsh new string sound, but you do get plenty of that "the strings are alive with the sound of music" tone. and isn't that what we're all after? ;-)
wade