Once dialogue or a vocal is recorded, prior to processing, some editing skills are required to help clean up pops, lip smacks, breathes or any other nuances the microphone may have picked up. Deleting long periods of silence is an obvious technique but slicing short pops that last for milliseconds at a time is surprisingly effective. Create clip fades on all audio clips to ensure the audio begins at the zero crossing preventing any pops when the playback head reaches the beginning or end of the audio clips themselves. Nuances may become a lot more present after processing which is why it is important that they are removed.
If there is no way of re-recording a bad vocal and you are stuck with what you have, some more advanced techniques must be used in order to correct those mistakes. Copying vowels or consonants and pasting them to replace other similar sounds is a technique sometimes utilized. Sometimes, articulation gets a little lost requiring the use of expansion to regain the dynamic range. Multiband compression allows you to zero in on a specific band of frequencies such as sibilance in the upper range. Using compression instead of EQ creates consistency within that particular range.
There will always be some level of noise in a recording. In some cases rumble, hum, mechanical noises (refrigerators or fans), ambience, vehicles or construction. The list goes on. Identifying the type of noise can help you reach for the correct devcice in an attempt to remove it.
Identify the frequency. Rumble or low frequency ambience can mostly be removed with a HPF but certainly may still be present further up the frequency spectrum. A noise that is consistent in pitch can be targeted with a bell curve or notch EQ.
Identify the overall amplitude. This helps you decide if you need a filter or a noise gate. Low amplitude signal that sit consistently in the background can be removed with gating. As the vocalist sings into the microphone the gate allows signal to pass through, and as soon as the vocalist stops, the gate will not react to the quiet noise based upon a predetermined threshold.
Often, noise is a wide band of frequencies which is impossible to remove with just an EQ or filter. With a gate. low amplitude signal will be silenced when the threshold has not been exceeded but will be let through while the vocalist is engaging the gate. Third party plugins are often required to help with wideband noise. Some act like a gate device while some require a sample of a clean piece of noise to reference in order to correctly remove it from the recording.
A combination of these noise removal techniques will greatly improve poor recordings.
Try using gate to eliminate low amplitude noise if you find there are a great number of slices and edits to be made to cut away silence.