Headcanon: You can tell what school of magic a mage uses by their hands.
Spirit Healers will always have soft and supple hands, using their staff very little to heal groups when one-on-one healing works so much better. Should they have callouses on their hands, they focus mainly on the fingertips and the dip of the palms, where pestles would he held to grind up ingredients, or where examinations would be performed touching as little of the sore spot as possible.
Blood mages have much rougher hands, littered with scars. They often cut the palm with a small blade to hide their blood magic until the last second, rather than use the open flesh and more flowing blood from the wrist. Their fingers often have a much more reddish tint to them, barely visible, stained with blood.
Entropy mages have much harder skin, changed to deal with the magic of death attempting to decay their skin. But Entropic magic is also about restoration, and thus they also have patches of much softer, newer skin in more sensitive areas of their hands, such as between each finger.
Creation mages have much softer skin, though not as soft as those of healers. There are scars on their hands, tiny little nicks from each spell gone wrong that has had the reverse effect to what they wanted, glyphs that have been turned against them by mistake. Their hands are often the most obvious to see, as Creation magic is hard to master, and thus accidents happen often.
Force mages have incredibly rough skin. Using such raw magic to aid them causes their skin to become rougher, the sheer power of the force spells toughening even their nails, making it almost impossible for them to gain any scars.
Elemental mages can have a variety of different hands, although it is very easy to catch them out; their palms will be too warm or too cold depending on the spells they use most, and their continuous use of a staff to aim such spells on a greater scale means that there are callouses on the bend of their fingers, where they grip the staff in their hands.
Primal mages have very strong hands, though their skin is often the weakest. They back up their flesh with rock armour and things from the world around them, leading the backs of their hands to be littered with scrapes where a Stone Fist has rubbed against the skin.
Shapeshifters are harder to determine, but can always be found out depending on how they hold things in their hands; the ability to change between man and beast means that they tend to hold things a little differently to most people. A spider shapeshifter, for example, would hold most items in the tips of their fingers, while a bear shapeshifter would hold it in the flat of their hand, fingers curled just enough to keep it in place.