My problem is that I bellow when I sing. I also run out of air from nervousness, but that's a problem that fixes itself after a few moments, most of the time. I can really tell when my vocal cords are relaxed and/or warmed up. Sometimes, I practice scat singing in the car, just sounding vocables, up and down, or any which way. I also always try to warm up my voice before I sing very much, which means some slow rising and falling notes. My loud voice is a blessing in some ways but I end up sacrificing pitch for volume, which isn't what I want. I've always had a pretty good ear, if I do say so myself, which has allowed me to hear harmonies very easily. This makes singing in song circles fun, because I can jump up or down into a harmony, but if the melody singer is picky, I end up doing more harm than good. However, no one has ever really complained, they just glare in my direction.