Do not use generic music just to fill the silence.
I was watching a film this year and it hit me that I had heard the song before. It was the same one I had used earlier in the week to edit a real estate video. It was free for commercial use and very generic; perfect for real estate, but not so good for a documentary. It was so plain that it kept distracting me from what the film wanted to say. I get it -- it is really hard to make independent films. The budget is minuscule, and you cannot always find talent that is willing to help out for so little. But if you cannot afford good music, don’t just use any song you find for free.
Do not force an emotion through music that you cannot match with the script and the visuals.
If your music is grand and swells up like the ending of a Hollywood movie, make sure your story follows the stakes. Do not put an action-oriented track or melodramatic violins in a scene if your character is alone and plainly framed in front of a computer. You might be able to pull it off, but it requires greater care. Music is supposed to aid the visuals, not engulf them (unless that’s the goal).
Ask yourself if having music is necessary in the first place.
Filmmakers are hammered with the importance of music in a movie - because it is important. However, it is crucial to remember that silence is part of the score too. It has incredible potency. For more on this, I'd recommend you watch Tony Zhou's video essay on this topic. While Zhou talks about fictional movies, my experience with the overbearing soundtrack, especially in reviewing work from this year, has been with documentaries. A few of them didn't have a single moment without background music. It was very distracting and it didn’t add anything to the story. I believe that, through editing, you can always find better ways to express a certain emotion and find a rhythm.