One of the biggest advantages to shooting RAW is the postprocessing. By making two conversions, each with different exposure values, you can get results as good as if you had bracketed when you shot. And since the images are exactly the same in every way except exposure, it's easy to combine the two to get one great picture with one great big dynamic range.
Adobe Camera Raw's sliders have confusing names. Translation: Exposure sets the white point, Shadows controls the black, and Brightness and Contrast affect the midtones. Stick with just one variable for a convincing composite.
When you want something lined up or squared off, think Shift. Hold it down when you're using the Marquee tool, and you'll get a perfect square or circle. Hold it down when you're doing a free transform or a crop, and the image's proportions will stay the same.