Try to shoot silhouette images when the sun is just above the horizon. choose the time around sunset because the sun causes the sky to be brighter than everything else for greater contrast. Use a narrow aperture (high f/stop) so the camera captures the whole scene with a high depth of field so everything is in focus.
Think about shapes. A silhouette needs to be a strong image. So, if you’re photographing a person, place them in profile, allowing more of their features to be outlined. If you’re silhouetting an object, you want to look for an object that has curves and angles that will stand out in silhouette.
If you are trying to create the effect with a point-and-shoot camera make sure you compose the photo with the background light by pointing the camera at the background. If you compose the image by pointing the camera at your dark subject, then the background will be over-exposed and you will not end up with a silhouette.