Add reverb to your vocal take. The reverb effect emulates the natural reverberations that occur in acoustically resonant environments. Reverb is similar to, but distinct from an echo. While an echo repeats the original sound, a reverberation is the persistence of the ambiance. It is a similar effect to singing in a cave or large, tiled room. The depth that reverb adds to a sound softens any harsh frequencies. Once you've saved your vocal take, select "Effects", select "Reverb" and set the "decay" and "feedback" settings high. A high decay lets the reverb fade away gently. The "feedback" setting governs the intesity of the effect. Setting these parameters high softens the edges of a digitally recorded vocal.
Adjust the auto tune parameters with care. Auto tune can save you time as it lets you correct minor flaws in pitch of an otherwise good take. If you elect to use auto tune, set the pitch and correction parameters low. The distinctly robotic vocal sound on Cher's song "Believe" was achieved by cranking the auto tune parameters high.
Set the compressor threshold to low. Compression is necessary to eliminate peaks and dips from your vocal. Without it the loud parts that you sing may distort and the quiet parts may disappear in the mix. However, over compressing your vocal takes away the natural dynamic range. When adjusting the "Threshold", "Attack" and "Decay" settings on the compressor, keep all dials as low as possible. Too much compression will your voice sound artificial.
Set the noise-gate threshold to low. The noise-gate eliminates background noise from the vocal track. Only sounds over a pre-determined threshold make it to the mixer. It's tempting to set the threshold high, especially if a cheap microphone is giving you noise problems. The down-side of this is that the first syllable of each line is attenuated. Click "Effects", select "Gates and Limiters" and select "Noise-gate." Adjust the virtual dial marked "Threshold" down from the default position.
Use a tube preamp. Vacuum tubes add natural warmth to an audio signal. This provides a welcome "vintage" sound amongst all of the digital technology of a typical home studio. Plug your microphone into the preamp and connect the preamp to your mixer with a quarter-inch instrument cable. The tubes will process the audio signal in a way that enhances your natural vocal timbre.