How can you distinguish between a plane, convex and concave mirrors?

Plane Mirror

Image formed is as far behind the mirror as the object is in front of it, with the lateral inversion of image. i.e. right hand side of object is left hand side of image and vice versa.

Convex Mirror

Image formed is always virtual, erect and diminished.

Concave Mirror

Depending upon the position of the object, size of the image formed can be equal to, larger than or smaller than the size of object. Also the nature of image formed may be real or virtual.