Different people have different arches, some are flat, others are high, and others fall somewhere in between.
Whether or not a runner overpronates or supinates all comes down to your arches. Runners who have low arches typically overpronate more than runners with higher arches, although this is not always true. Typically, an overpronator's heel strikes the ground first, on the outer (or lateral) side. Then, as your body's weight comes down, your arches collapse, allowing your foot to roll to the inside (or medial side). Take a look at the wear pattern on the bottom of your current running shoes.
Overpronators typically wear out tread on the outer edge of the heel, and the tread near the ball of the foot. Supination is the opposite. Supination happens when your foot strikes the ground on the outer edge of your heel, and instead of your arches collapsing in, your feet do the opposite and roll slightly out. Again, looking at the wear pattern, the outer edge of the heel should be wearing out, as should the tread along the outer edge of your foot. Ideally, runners need shoes which don't allow them to overpronate or supinate, but be kept in the Neutral position.
Knowing your arch type, body type, and fitness goals we can start fitting you into different shoes. We'll watch you run and walk in several different options on a treadmill, analyze your gait, and use that information to determine what will work best for your specific foot type and needs