Remove excess audio from the vocal tracks. When you record a clip, the microphone will pick up background noise before and after the singer performs. Use an envelope, cutter or clip margin tool to remove these areas of unwanted noise.
Listen to each clip independently for digital imperfections or background noise, such as clicks and pops. Use a wave-form editing tool (usually called a pencil tool) to redraw the spikes in the waveform that cause the pops, making it smooth.
Insert a de-esser effect into each of your vocal tracks. A de-esser removes "plosives," or the bursts of air caused by hard consonant sounds. If your effect comes with presets, use one of those; if not, set your de-esser to a moderate setting and listen to the singer. Sweep the dial around and listen for when the hard "s" and "t" sounds are limited without compressing or cutting any other sounds from the audio.
Add equalization to the tracks. For male vocals, boost the low midrange slightly and be careful of low and high range, which can make the audio muddy and brittle, respectively. For female vocals, the upper midrange and high range are important, but be sure to keep lower midrange foundation. Use your ear to tell you what sounds good for the particular singer.
Mix the tracks with the rest of your audio, adding other effects, such as reverb and delay, as they fit with the song.