Most distortion in vocal recording comes from preamp overloading, so make sure you have one that can handle your the input. Call recording studios and ask what kind of preamp they use, and you'll get a good idea of what to look for.
Remember that microphones are made for different purposes, such as recording a guitar or recording drums. Select an omnidirectional or ball microphone, which picks up sounds from all directions. Using an omnidirectional an microphone compensates for any movements the singer may make while recording because sounds from all positions will be picked up.
Place the microphone six to eight inches away from the singer -- any closer and the microphone may distort; any farther away and it may pick up room sounds. Instruct your singer to "work the microphone" on big, high notes. This means moving away from the microphone so the sudden change in volume won't overwhelm the equipment.
Resist the temptation to add reverb while recording your singer because it may result in muddy vocals. You can always add reverb while mixing. If your singer wants reverb in the headphones, provide it without recording. Treat equalization the same way. Don't emphasize high or low tones with your equalizer; just record the natural tones and emphasize what you want during mixing.
Fix any phrases or passages during the same session as the original vocals. Waiting for another day may mean losing the sound you have established due to changes in the vocalist's vocal chord condition, changes in the way the microphone is set up and changes in levels on the soundboard.