btw, you need smoke, mist, or haze..
basically things that act as a "screen" for the light.
that is for that kind of situation..
if you have nice enough clouds, you can get what are termed as god's rays as well:
like jopel says.. right place, right time!
for god's rays, if you want a foreground, then you might possibly need a means to balance out exposure. if you don't know what i mean, go out, shoot more, think more.
for the means, a gnd filter helps, hdr can help if you do it nicely enough, digital blending can help.