Here's a fantastic breath support exercise that will help you practice proper support and identify weaknesses in that area. It may seem a little silly just out of the gate, but rest assured that even professional singers do this frequently, often as a warm-up exercise. Let's jump right into how to do lip trills, and then we'll discuss the benefits. (NOTE: I recommend doing the epigastric bounce exercise in the previous entry before attempting lip trills.)
Stand comfortably with your feet shoulder-width apart, shoulders slightly back, with your sternum (breastbone) elevated. Don't arch your back, lock your knees or adopt a "ram-rod straight" posture.
Release your jaw and let it just hang there. Keep your lips lightly closed. There should be space between your upper and lower teeth, and your soft palate should be raised as if you were about to yawn.
Open your lips and allow air to fall into your body by releasing your abdominal, side and lower back muscles.
Close your lips gently; keep your teeth apart and your throat open.
Engage your breath muscles and release a slow, steady stream of air on any pitch of your choosing. Make sure your sternum stays raised! When this is done correctly, your lips will vibrate. I've heard this sound referred to as a "baby motor", because apparently people do it to make babies laugh. (?)
A few comments on the above: first, you can practice lip trills on a pitch, or with no pitch at all. I recommend starting with a pitch, as this further regulates airflow and makes it slightly harder to waste air. As you gain proficiency, you'll be able to do this without musical pitch.
This exercise is difficult for most singers in the beginning, so don't expect to do it perfectly right out of the box. If you can't start any vibrations whatsoever, you may have tension in your lips, and/or you may be depressing your sternum rather than engaging your abdominal muscles. If you achieve vibration initially but it quickly peters out, it's often because you're collapsing your chest/sternum (and possibly disengaging the breath muscles at the same time).
Once you can reliably create and sustain a lip trill on a single pitch, try progressing to short melodic patterns such as "Do-Re-Mi-Re-Do". Don't worry about reaching the extremes of your vocal range at this point; stick with whatever's comfortable for your voice on that day. I'd also recommend practicing this every day, but only for a few minutes. Unlike instrumentalists, singers can't physically practice for six or eight hours a day, even if they have the time and desire. It's just impossible — and that's okay. It's the consistency of daily repetition that is key, even for singers who usually only sing one or two days a week. A few moments of thoughtful vocal exercise every day improves the entire choir and makes the worship of almighty God more beautiful, and we singers have a sacred responsibility to put in that effort. God and His angels will provide the rest!
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