The Navigator tool in Photoshop is one of my favorites and it seems to be largely unknown. Most of the time, I see people review images by zooming in to view the image at full resolution, moving around to look at different areas, and zooming back out to see the entire image. The problem with that is you can easily get lost in the image and end up missing flaws that should be fixed.
The Navigator prevents you from losing your place, as it were, by showing your location within the image while you zoom in & out and move around. I tend to use the Navigator on a second display, but it is a panel and it can be moved, resized and saved into any custom layout you choose.
This image is currently fit to my laptop’s screen and is being viewed at 22.67%. That resolution leaves a lot of room for errors when working. I usually zoom in to at least 100% and generally zoom in much more. But there is still a lot of room for me to completely miss problems in my image.
To bring up this magic tool, go to Window > Navigator to bring up the Navigator panel. Your position on the image is displayed by a red box. This box can be clicked and dragged to move your view of the image when zoomed in.
The real power comes when you move by precise quadrants, which keeps you from missing any problems with your image. To move up and down, section by section, use the Page Down and Page Down available on a Mac keyboard as fn + the up or down arrow keys. To move view right and left, use Control + Page Down or Page Down on a standard Mac keyboard fn + the up or down arrow keys + Command.
Take a look at the final image and all many of my other photos on Flickr.