Typically, all communications in an open source project (except sometimes IRC conversations) are archived. The archives are public and searchable, and have referential stability: that is, once a given piece of information is recorded at a particular address, it stays at that address forever.
Use those archives as much as possible, and as conspicuously as possible. Even when you know the answer to some question off the top of your head, if you think there’s a reference in the archives that contains the answer, spend the time to dig it up and present it. Every time you do that in a publicly visible way, some people learn for the first time that the archives are there, and that searching in them can produce answers. Also, by referring to the archives instead of rewriting the advice, you reinforce the social norm against duplicating information. Why have the same answer in two different places?
— Karl Fogel, Producing Open Source Software