outreaching is where most of the work is done, and there are many tools you can use, although none is really needed. the point is making good questions to ask them on their field of expertise, so you'll have both great content to compile and an audience who will love to hear other experts feedback on that same question.
the steps are in much detail although not really so well described in this ugly link, but I promise getting aware of the core idea there is very interesting.
I haven't done it myself just yet, for it is a lot of work and, well, I couldn't set my mind to do it. But I will, and it will be awesome!