Maybe this is nothing new to all the Audio guys over there, but to must video editors I know it will help on getting the best of the audio when things aren't that great.
Quick tip #1
Audio Noise Cleaning
1. load your audio file into Audition (i know there may be a similar effect/plugin for other app)
2. Select the file and copy it to a new one (you need the original for later) save it and let's start with this part.
3. under Effect menu scroll down till Stereo Imagery, then select Center Channel Extractor
4. play with the settings until you eliminate the entire voice in the file (this works best for live events where you can't get a clean line or even when you do but need some corrections)
5. load the whole file as a noise profile by selecting all the wave and by right clicking under Capture as Noise Profile.
6. Select your original track (alternative you can open it copy it and paste it on a new one so you always keep the original) then go to Effects, Restoration, Noise Reduction
7. here your file will load with the noise profile captured before and you will get a very clean audio, fine tune as need and enjoy!