Clouds at Blackcomb Mountain, Whistler, British Columbia, Canada
Minolta A2, 28-200mm built-in lens, f/7.1, 1/400 sec. Hand-held, P Mode
I took this photos during a ski trip to Whistler in Canada in 2006. As I was descending down from the top of the Blockcomb Mountain and looking into the sun through my goggle, I saw the golden sunlight peek through from behind the clouds, bring out this very unique quality of the transparency of the clouds - you can seen through the clouds and spot some details of the mountain and trees on the other side behind the clouds, and the clouds were lit up by the afternoon sunlight along with its warm color.
Had this photo been taken from the opposite direction, pointing the camera towards the clouds at the same direction as the sunlight beaming towards the cloud, the clouds would not have this unique sense of transparency.
Eve since then, whenever I was out photoing clouds, I often look for the possibility and opportunity of shooting the clouds while facing the sun, position the sun behind the clouds, to bring out this magic of transparency. In many scenarios this will add the drama to the scene, making otherwise a dull image into a fascinating one. You should try to do the same whenever you are out shooting, looking for opportunities whenever the sun is behind the cloud and light up the clouds, and make that part of your photo's key elements.