Create a template of how a good question should look like. This is becoming more and more popular on Github's issues, not sure since when, but I'm definitely seeing it more often these days. Include sections like "what did you try" and "where did you look and what results came up", among others. Auto-close questions that don't use the template; if it's automatic, you're less likely to become a target of hostility due to this.
Set up a process of converting questions into docs (wiki works). If a question's quality is too low for its answer to be put into docs, delete it. If it is good enough, make an effort to answer and make it easy to contribute it to the documentation. Make sure it's easy to find both Q and A afterward.
Make sure you have a "troubleshooting" section in the docs. Try to assist people with finding the answers on their own as much as you can, but also make sure it's trivial to tell if someone actually read that section and followed the steps outlined there. If you get a question from someone who obviously didn't care to read that, delete it.
Make sure your docs are indexed, searchable, and that you're able to link to specific paragraphs (ideally) or at least headings (but then make sure to actually use headings that make sense). The more precise you are when telling people where they should go, the less likely they are to come back to you to ask again.
In general: make sure good questions (and their authors) are rewarded and make sure people who don't want to put in the work to make their questions good are easily distinguished. Warn the latter once or twice, then punish swiftly and decisively if they don't improve.
Above all else: don't expect your answers to be valued if you, yourself, don't value the time and effort expended to give them. Just because you know something doesn't mean everyone and their cat is entitled to be coached by you. Make it clear that getting an answer from you is a trade: the one with a question has to put in enough time and effort into asking it for you to find it worthwhile to spend your time and effort to answer.
Beware of jerks. Just like you can construct malicious packets that make the receiving server do a lot of work for nothing, it's possible to craft questions that amount to a DoS attack on you. Manage the time spent on answering questions and track it. If servicing a single person takes too much of your time, become suspicious. Taking too much of your time may just be their goal.
Finally: recruit helpers. People who often submit good quality questions probably dislike low quality questions as much as you do. Let them help you filter out the noise.
My 2 c.