Instructions
Rotate the mode dial on the top right of your camera body to "Av" or "A" to engage aperture priority shooting mode. This mode lets you select your desired aperture while the camera selects a shutter speed that will provide proper exposure.
Turn the knob on the backside of the camera's hand grip to the left to widen your aperture. On most lenses, the background will begin to blur smoothly at f/4. For a completely blurred background, use a very wide aperture of f/1.7 or f/2. This will also soften the facial features of your subject for a flattering portrait.
Look through your viewfinder and compose your shot. Depress the shutter button halfway to automatically focus on your subject. While working at very wide apertures, you may also consider using manual focus instead of autofocus.
Stabilize the camera and press the shutter button all the way down to take your picture. Review your shot in the LCD screen and reshoot if necessary.