Choose Crop tool from tool palette (C)
Normally, select Use Photo Ratio as the Aspect Ratio, but you can change it if composition or paper size require it
When you have the composition right, click the green arrow at lower right.
Check to see what has happened to image size. (Use Image->Resize->Image Size.) If you used “Use Photo Ratio” the image is automatically upsized to what it was before you cropped. Otherwise it is cropped to the size you set.
