I'm occasionally asked about how do I get "That Sound" on my acoustic guitars...
The answer isn't always straightforward, I always advise to play with long finger nails on the picking hand, this effectively gives you a plectrum on the end of each finger, and as a result a clear, crisp note is heard, however some songs benefit from different approaches, I sometimes stroke the strings with my nails and this gives a lovely sound as used by Missy Higgins on "Forgive Me" (below)...sounds like she recorded it in the bathroom where the huge bust up took place...
Paris Alexander (a talented musician and a member of CPM website) also uses this technique to good effect.
I use thin Martin plectrums for strumming as the bending adds something to the sound of the strum, (I never used to use thin plectrums but found they open up the track in the mix better)
New strings always help, I was put on to Thomastik by Adam from the UK Songwriters forum, and they seem to perform well, although I can recommend Heritage Series Strings by Newtone. (Exceptionally clear tone and very easy to play)
Hope this helps, let me know what you swear by...
Rich