Commands mentioned:
nG - jump to line n
L - jump to the bottom of the screen ("low")
H - jump to the top of the screen ("high")
M - jump to the middle of the screen ("middle")
C-o - jump back
C-i - jump forward
zt - move this line to the top of the screen ("top")
zb - move this line to the bottom of the screen ("bottom")
zz - move this line to the middle of the screen ("ziddle?")