This doesn't mean you need to stay completely silent, but if you do interject, look for natural pauses to ask open-ended questions that benefit the speaker, not just your curiosity.
If he didn't do it, why would he need to fake his alibi? - Because he's a kid and he was scared. - Angie, this is not a good idea. - I-I just gotta say this.
After the married women spoke about how hard it was to balance their lives, the single woman interjected that she was tired of people not taking her need to have a life seriously.