You've already launched your product now it's time to set up a "self-service" help page for your users. Why?
According to Forrester, "72% of customers prefer self-service to resolve their support issues over picking up the phone or sending an email." Our own studies show (we keep an eye on these metrics since we're selling a helpdesk ticketing app) that up to 45% of support issues can be solved without contacting support. Of course it varies throughout specific niches and industries, but on average it's 45%. Which means - almost half of your support burden can be lifted.
Include routine and repetitive questions in your FAQ and stay short and sweet. Things like changing email or adjusting the billing info - let the customer do these simple things on their own. Remember to add screenshots, they help a lot
Just launched? Have no idea which questions will become "repetitive"? No problem. Show your app to your colleagues. Show it to your friends and family members. Write their questions down and put those on your website.
Keep the paragraphs short and clear, mind the headers and formatting to make the text easy to read. Don't be too technical. Cognitive psychology studies show that presenting small chunks of information is a great strategy for organizing and prioritizing information, making it easier for users to understand it.
No matter how detailed the FAQ is or how structured and organized things are, some people will still prefer using the search button to find an answer. Make the search box big and fancy, place it "above the fold" on your page. Use Google's site search if you don't have your own engine, it's pretty easy to set up, you can even customize the design and all.
Your manuals and FAQ pages will attract a lot of "long tail search" visits. So publish as much internal content as you can - installation manuals, readme's, configuration walkthroughs, use-cases, tricky setups and non-trivial configuration steps - everything you have should be published online. Google loves it.
If you have an installation video - publish the transcript. Same goes for your podcasts, infographics and other "non-text" content - everything should have a text-version.