I don't believe it's possible to increase vital capacity; the size of your lung is the size of your lung.
That said, it's definitely possible to increase the percentage of your lung that gets used while breathing.
I've been using an ultrabreathe before practicing to remind myself to take a full breath, and I use an inspirometer to help with breath control, making me take slow measured inhalation. Both of these things have been quite helpful in my breath control. Oh, and also getting off the couch and doing some cardio... I'm still working on that one!
Mike Taylor
Illinois Brass Band
Fox Valley Brass Band