On my all my workshops, "Check Your Histogram" is the daily chant.

Your camera's histogram is your light meter. It will tell you if parts of your image will be overexposed and if the shadows will be blocked up.

The basic concept is to "move the histogram to the right." You do that by increasing the exposure until the "mountain range" (which shows the distribution of light levels) is mostly on the right - but without a spike on the very, very right. Most of your image data is on the right, which is why your want your histogram on the right.

Photographs © Rick Sammon

If you do get a spike, the brighter parts of the image will be overexposed, as illustrated by the picture on the right. The image on the left is properly exposed - you can see details in the white feathers.

If you do get an overexposed area in an image, you can try to rescue it with the Shadow/Highlight control in Photoshop and Lightroom. But it's best to get the best in-camera exposure - by checking your histogram.

Explore the light,
Rick