I rarely comment the code itself, but I tend to explain what functions do and write huge lines that explain where in the code I am so I'll find it quickly later instead.
Python example:
# # # # # # # # # # # # # # # # # # # # #
# ------ IMPORTS ------------------------
import foo
import bar
# # # # # # # # # # # # # # # # # # # # #
# ------ ENCRYPT ------------------------
# ---- Encrypts text, etc. --------------
def encrypt(blah):
# blah