Mastering contrast: Shadows/Highlights
You'll note that under the Enhance>Adjust Lighting menu, there are two other tools worth mentioning: Brightness/Contrast and Shadows/Highlights.
The former does exactly what Levels does, but without the benefit of being able to see that tone mountain, which for most photographers is enough encouragement not to use this feature. It's also regarded as being a destructive form of editing—too much use might damage the pixels irreparably, so I'd not recommend using it.
The Shadows/Highlights tool can be very useful for rescuing tones that might appear lost in the highlights and the shadow areas, for boosting details in the darkest parts of the file. Some care must be taken with this feature because too much will make the result appear fake.
Remember that if you are doing this on a JPEG file, it has already been processed in-camera, so if there appears to be no tone in the lighter parts of an...