First things to do when ImageJ opens :

Brightness & Contrast Tool : (Shift + C)

Channels Tool : (Shift + Z)

Built-in image navigation available with any tool :

Shift + wheel = zoom in / out

Space = hand tool

With hyperstacks : (more than 3 dimensions (channels , Z slices or frames) )

wheel = set active channel slider

space + wheel = move Z slider

If you need to see big Images :

Drag and drop the image just above the “more tools” button on the far right : >>

it will open the files as “Virtual Stacks” : only the currently displayed slice is loaded into the RAM

This is read only, changes won’t be saved.