Here's a nice little ditty that I read in Laura Ingalls Wilder's Little Town on the Prairie. Ma (Caroline Ingalls) wrote it in Laura's autograph album in real life (I've seen the original album, by the way ;-) ). The poem is short, but full of truth.
"If wisdom's ways you wisely seek,
Five things observe with care:
To whom you speak,
Of whom you speak,
And how, and when, and where."
These are things I've been learning in my daily life. Now if I would only remember and apply them!