if your gizmo disappears press X to bring it back.
press Q repeatedly to switch between selection modes (lasso selection saves my day all the time
)
you can Zoom in witout have to rely on the mousewheel steps just press control+ alt and left click and drag the mouse. this way you can zoom in smoother.
if you want to pan in the viewport press ctrl to move faster. also if you move something press ctrl so it gets "boosted"
Right click on a roller will reset it to the default value. (mostly 0)
selecting something and pressing Z zooms into the object (much like the F in maya)
if you loose the rotation point and the cam in the viewport just goes crazy press z so you can zoom in into your selection and rotate around it. if you do not have selected anything it will zoom out so you can see the entire scene.
There are different right click modes
try it with
shift + rightclick
ctrl + rightlick
ctr+shift + rightlick
alt +rightlick
...
...
and so on.
you will be amazed how much you can get out of the quad menues with customisation.
have a shortcut for hide or freeze objects on
shift + D(issapear)
shift + F(reeze)
fastens up working in a heavy scene.