RTFM, GIYF and - my favourite - STFW
OK, we all get annoyed by people asking inane questions, when a moments’ effort could find the answer.
In days gone by, you’d tend to tell the questioner to RTFM (Read the ‘Fine’ Manual).
Now?
You’d tend to tell them GIYF (Google is Your Friend), or in egregious cases STFW (Search the ‘Fine’ Web).
A better way might be to provide them a link to STFW which politely tells them this. If you’re feeling particularly subtle, you can of course use something like tinyurl.com to obfuscate the link a bit.