Give your supporting characters unique talents that fit your plot so each contributes something to the story. This enhances their individuality and helps avoid redundancy in your characters by justifying their existence in the story.
If you’re not sure what I’m talking about, think about your favorite sit-com and the differences between the characters. These traits are also useful for creating conflict. Weird habits or talents can also be useful in describing their appearance and contribute to imagery. For example, if someone is a mountain climber they’ll have a different appearance than someone in a garage band.