Sound editing is important in films because it helps immerse the audience in the environment. It can also be used to add more emotion to a scene, and increase the realism of a setting. Sound
editing is one of the main factors that help give a film a more interesting aspect, and a better final form.
If there are any concerns on a set, stop and solve the issue. Allowing time gives you a better chance for better sound, meaning you don't have to edit as much.
Pick a good team, so the sound recorder, cameraman and presenters all work together instead of a mishmash of problems arising and causing need to re-record everything.
If people speak softly or have an accent, record them as early in the sequence as possible, showing their face and lips moving to help people watching understand them.
Pick appropriate music. Action music for a country shot is not appropriate.
Bring in someone else to listen to your clips, someone that hasn't seen or heard it before. If they don't get something, they'll tell you.