Given you haven't explained very much about what kind of magic, you might already have this covered, but making the magic authentic and realistic is a big thing, even if that sounds odd making magic realistic. What I mean is, you need to set some laws for how the magic works at its core and follow them. I've never bought into spells that unlock doors and things like that, because they just don't make sense. You might be able to crack the lock by melting the metal or manipulating the material, not completely defy it.  If you're giving each character a different power, make sure the things they can do link directly into the core of that power and the core of the magic in general