The Histogram is now interactive in Camera Raw. Instead of selecting the sliders in the Basic panel, simply click and drag on the Histogram to adjust the Blacks, Shadows, Exposure, Highlights, and Whites. The video below demonstrates how.
In addition, Control -click (Mac) | Right Mouse -click (Win) within the Histogram to enable Lab color readouts, even when the Workflow Options are set to another color space (such as Adobe RGB). Note: the context menu can also be used to toggle the shadow, highlight, and gamut clipping warnings.
In this video tutorial (Develop Module Advancements in Lightroom 4), you’ll learn how to create the highest quality photographs by taking advantage of new and improved global and local adjustments in the Lightroom 4 Develop module.