If you are interested in human consumption, there's "free --human" which decided on useful units by itself. The "--human" switch is also available for "du --human" or "df --human" or "ls -l --human". It's often abbreviated as "-h", but not always, since that also often stands for "--help".
Thanks, I generally use free -m since my brain can unconsciously parse it after all these years. ls -lh is one of my learned commands though. I type it in automatically when analyzing things.
ls -lrt, ls -lSh and ls -lShr are also very common in my daily use, depending on what I'm doing.
