Sometimes you also need to look at an object or scene from the bottom, from behind or from the left. These keys will help you:
You know to use the 1, 3, and 7 keys on the Numpad to change views. To see from the opposing angle of a view, you press the Ctrl key and the number for the view on the Numpad. Ctrl+7 shows the bottom view. Ctrl+1 shows the back view and Ctrl+3 shows the left side view.