Rule #2 – Maintain Consistent Levels between your edits.
So your routine starts with your voiceover introduction that you recorded on your iphone, then you sampled some dialog from “The Dark Knight” before you put in the beginning of Carmina Burana’s “O Fortuna” which fades into an underground track that your buddy in Turkey sent you from an 8-Track that he found in his uncle’s basement? I hate those routines. The least you can do is make sure that your levels are consistent in the final product.
Your editing software should allow you to view the waveform of your final product. This is a visual representation of how your music will sound. Big peaks are big sounds. Valleys are quiet. Look at the overall balance of your music, and make sure that it doesn’t suddenly jump from quiet to loud unintentionally. For example, a gunshot should be very visible on your waveform. Most other things should not.