Our Strobist portrait setup step-by-step: 5-6
05 Ambient exposure
Your camera exposure controls the brightness of the areas of the scene the flash doesn’t reach. Set shutter speed and aperture in Manual mode so that the background exposure is about two stops darker than the built-in meter suggests. Make sure shutter speed is below 1/250sec.
06 Flash stand
Use your tripod as a lighting stand. Some flashguns come with a foot that allow them to be mounted on a tripod (if not, try a £9.99/ $12.99 Frio coldshoe).
Rotate the flash and its head so the red circular window on the side of the flash points at the DSLR’s pop-up flash.
To tweak exposure, adjust the flash brightness using the flash exposure compensation facility on the camera itself. Make the background lighter or darker by adjusting the shutter speed.
Snoot lighting: how to take moody Strobist portraits using your hotshoe flash
Flash photography tips: external flash techniques anyone can understand
How camera flash works: free photography cheat sheet
Flash compensation: how to get perfectly balanced exposures
Flash portraits: creative off-camera lighting techniques you have to try