I would modify this slightly, and suggest finding out who some of the most highly regarded programmers are for your language, and reading their libraries.

Standard libraries are often a very mixed bag of stuff because things are added but rarely taken away. Some it may be very new, and some of it may have been written before the idioms of a language were even finalized, and then frozen by compatibility needs. If you don't already have a strong sense of good style (or what is currently considered good practice for a language) you may find it difficult to identify what is good and what is a relic of history.