That's the age old problem with photography -- as a human, we can see what? About 11 stops of light whereas cameras are limited to about 3 or 4 stops of light in a photograph. If you shoot a subject against a bright sky, you can do one of two things:
1) Have the sky properly exposed and the subject in silhouette.
2) Have the person properly exposed with the sky blown out.
To remedy this, you have a couple of options:
1) Drag the shutter -- meter for the sky and add a flash to light the subject so you have both properly exposed.
2) Use auto-exposure bracketing to get multiple captures at different exposures, generally one at normal exposure, one two stops over and one two stops under. Then, use Photoshop or a program like Photomatix to composite the images to get the highlights and tone across that great range of exposure.
I'd wind up using #1 if I was shooting people and #2 if I was shooting landscape. That's my personal preference, of course.
