Various tasks are commonly used when sorting and rating images in Lightroom. These are my favorites.

G – Grid view in Library
E – Loupe view in Library
C – Compare view in Library

P – Set the Pick flag
U – Remove Pick or Reject flag
X – Set Reject flag

0-5 – Rate the image 0 starts to 5 stars
6 – Assign red color
7 – Assign yellow color
8 – Assign green color
9 – Assign blue color

-> – Next image

Ctrl G – Stack Photos
Ctrl Shift G – Unstack Photos

Ctrl + – zoom in
Ctrl – – zoom out