I have mentioned this several times already in the short life of this blog, and I know I will mention it dozens of more times:
Sound is the most important part of your film
And I have found a brother in arms over at BleedingCool.com. They are running an ongoing series on making your film. They are up to part 20(!), where they discuss sound.
Writer Chris Hood covers the whole gamut, from on location production sound, to looping, to scoring, to track separation.
It’s an awesome read!