I have my standard way of zooming in or out of an image in Photoshop. That is with the ctrl + or ctrl - keys. Clicking the key combination's one at a time will allow me to zoom in or out in small steps. What you might not be aware of is that if you hold down the ctrl and plus or minus key you will zoom quickly in or out of an image. This might be helpful if you need to get down to the individual pixels very quickly. And as a standard you can double click on the hand tool to reposition your entire image in the canvas space.