Audio is critical to a high-quality video production. Most important is the original footage. Take some extra measures to ensure high-quality audio. Select the right mics for the job, turn to wireless audio if the budget allows, and use professional voiceover techniques.
Some standard, news-style audio-editing styles will take your audio one step higher. Use cross-fades, L- and J-cuts, and cutaways to give your piece a quality "feel." Use the Audio Mixer to adjust the levels of more than one track at once to bring sound under a narration and then bring it back up during narrative breaks.