First, the only change from Lightroom 1 to Lightroom 2 in regards to the crop tool is its new home. It moved from the Develop module’s Toolbar to the new Toolstrip under the Histogram.

You can still jump to the Crop Tool from anywhere in Lightroom by selecting a photo and pressing R.

Once you are in the Crop Tool you can choose between different crop overlays to help you find the strongest composition by pressing O to cycle through them, or look under the View > Crop Guide Overlay menu.

Read Advanced Cropping over at peachpit.com.