For me, I find that figuring out a characters theme music or musical style helps with being able to effectively write the characters personality. Just hearing the opening riff to Come As You Are, for example is a good writing boost for my current Main Character.
In my experience, knowing a characters musical tastes can determine and tell you a whole lot about their personality. For the character I'm writing for currently, there's a whole lot of 70's/80's hard rock metal ( AC/DC for example) with a smattering of early 90's grunge thrown in.
Those types of beats and instrumentals, not so much the lyrics, put me in the mind of having a very hard edged personality. Sort of an in your face take no prisoners, charge in head first without thinking sort of thing. Mix that in with some pretty heavy weaponry and a propensity for dangerous situations, and you can quite effectively build a background around the person that's realistic to the world they live in.
My own military experiences lead me to a bit of bias towards characters with similar experiences, but when you're dealing with a world that has a lot of supernatural elements, vampire and werewolves for example, having that as part of the core of who the character is does tend to be useful.
Mostly because how it colors their mindset and how they're going to approach situations. Makes me think this character is a hammer who is going to see every problem as a nail. Subtlety probably not going to be her strong suit.
I've already described her in writing as a "bull in a china shop", so it's coming along nicely in my opinion. Makes writing interactions with other characters especially fun.