One of the easiest way to visualize ray diagrams for lenses is by using an array of arrows on the board as the object and the camera on your phone as the screen.
(i) Convex Lens : Arrows on the board are placed outside the focal length of the lens -> Inverted image
(ii) Convex Lens :Arrows on the board are placed inside the focal length of the lens -> Magnified Erect image
(iii) Concave Lens: Irrespective of whether you place the arrows inside or outside the focal length, you get an erect image.
(iv) Convex mirror: Virtually erect image formed from a Christmas ornament
The following video from UCLA extends the ray diagram analysis for concave and convex mirrors: