I find myself using this often while debugging errors or trying to figure why a server is slow or unresponsive.
# show all processes
top
# to quit top type q
# to sort press Shift+O
# K for cpu % or use Shift+P
# show all processes from a specific user
top -u username
# example for me using deployer as the user to run web processes
top -u deployer
# highlight working process
z
# show path for process
c
# kill pid
k
# get help
h