Shortcuts are a great way to save time when working in Illustrator. Here are some simple ones that I use most of the time.

 repeats the previous action.

  duplicates what is selected

makes the object have no colour in the fill/stroke

 Switches the fill and stroke

direct select

 selection tool

rotate

 pen

add anchor points

take away anchor points

eyedropper tool

Paste In Front 

Paste In Back
                         to Paste In Place

to zoom in

zoom out