Follow the shadow
Place the lamp opposite your writing hand and check where the shadow falls across a notebook. Move the head rather than simply increasing brightness. A broad pool of light is usually easier to work within than a tiny bright spot surrounded by darkness.
Check the screen from your chair
With the display showing a dark page, look for reflections of the bulb or shade. Move the lamp sideways until the reflection clears your normal viewing area. Keep some comfortable background light in the room so the desk is not an isolated bright island.
Choose useful adjustments
An adjustable arm needs to stay in place when released. Check whether the base uses valuable desk space or a clamp fits the actual tabletop thickness. Test the control with one hand; a touch switch hidden behind a monitor is inconvenient no matter how elegant it looks.
