Silhouette is photo with the main object which is totally dark and the background is bright, so you can see the shape of the main object . Shooting silhouette isn't so hard if you've already known the steps , they are :
Switch off the Flash
The first and important thing that you have to do is switch off the camera flash, if you don't do it you will get standard photo (because its main object isn't dark). So switch off first!
Find the Good Lighting ( backlight)
To get awesome silhouette photograph, remember that the background must be brighter than the main object. That's why most of people usually shooting silhouette at sunset or sunrise, where the sun (light source) is in the behind of the object that you want to shoot (Backlighting). But! photo silhouette can be made whenever, you just need to explore and train more. The point is you must find the brighter background than the main object.
Find the impressive and unique Object
Silhouette photograph very accentuate the shape of main object, so just find the object which is have impressive , strong , and uniquely shape. Take a look the photo above, because the main object lost some detail and become darker, the shape is more stunning. We can see clearly the border of the body shape, you can try to the other objects definitely.
Find the suitable background
To get amazing silhouette you must find the bright background. Also Try to find interesting background but isn't so crowed in order to show up the main object. Sky and beach is the most favorite.
Measure the Exposure ( manual/auto)
As can as you can do, use the manual exposure. Set metering in spot metering. Measuring in the brightest background. In photo above, i measure the sky light over head. Change the aperture and shutter speed as you want ( big aperture for blurry background and small aperture for sharp background). After you've determined the aperture and shutter speed, direct the camera to the main object. Set the focus point on the main object,then press the shutter button.
If you don't use manual mode, you can still use auto mode. Direct camera to the most bright area, in the photo above is direct at the sky which is above the tourist. Half-press the shutter button ( don't full pressing) hold the shutter, direct camera to the main object, then full press the shutter button.
Don't be Afraid to Try
Try the different combination of aperture and shutter speed if you've failed in the first chance. Try to do experiment with the object around you, don't stuck only on sunset and sunrise, because the silhouette photo can be made everywhere.
Best of luck!