by Julieanne Kost
When I finish an image and am confident that I will no longer need to move/reposition/resize layers, I choose Select > Select All and then Image > Crop to trim any extra content that extends beyond the image’s visible canvas. This is a permanent change, so be sure that you are willing to commit to deleting everything outside of the visible image.
Another method would be to select the Crop tool in Photoshop CS6, check Delete Cropped Pixels in the Options bar, and tap Return/Enter. Photoshop will display a preview of the image area that extends beyond the visible canvas (so that you know what you are cropping). Tap Return/Enter again to apply the crop.
Note: When working with Smart Objects, any extra image that extends beyond the visible canvas will not be deleted.