Control + = to zoom into the picture
Control - = to zoom out of the picture
Z = give you the magnify glass to zoom in or out
Holding space bar = gives you the hand to pan to left ,right, up, or down around the page.
Plus other short cuts for navigating Photoshop.
Here is a quick video tutorial on how to navigate Photoshop for all you newbies out there. Hopefully this is helpful. You can instantly download the Photoshop video course by going to the store. http://www.creativelogoart.com/store2ps.html