Look into it NOW. You'd be amazed at how much this process helps, and not is NOT just for "mild" asthma at all. Much of the studies down were with people suffering for asthma at all levels. There are a lot of videos for the Buteyko method on youtube.
The science behind it just makes absolute sense and the results can not be ignored.
I don't practice Buteyko breathing, but there are many websites that can certainly get you started. From my understanding, these exercises are good for people who have mild asthma. The theory is that people get stuck into a pattern of over breathing, and by doing the exercises you can retrain their lungs to breath a more normal pattern.
http://en.wikipedia.org/wiki/Buteyko_method