I find a glass of Irish Cream helps a little bit, but the soundest advice is to find folk venues without smoke. In many areas, this is easier said than done and you may find yourself having to be proactive about organizing house concerts and the like.

As Clinton pointed out, we wheezy types in the audience do miss out on an awful lot of great music because it's not safe for us, healthwise, to be in the environment in which it is to be performed. We wheezy types of performers miss out, too, on the money to be made for bar gigs (lots more $$$ than smokeless-coffeehouse gigs)!