I don't know how other people do it, but when I stream I have my twitch, youtube and facebook accounts linked to my PS4. I hit the "Share" button on the controller and go to Broadcast and set the options from there. Options like public or friends only invite links, having the chat menu on the side of the video, the title. I don't know about streaming on the computer, I know most streamers use cameras and mics for their set ups. The hard part is actually getting viewers. If you want to get a lot of viewers or at least viewers in general, the best game to stream would be a game that just came out and is popular, something like Overwatch.
I'm not a huge streamer, I just stream every now and then, then I send the video to my youtube account. The last game I streamed was The Walking Dead: Michonne parts 1, 2 and 3. I've also streamed Batman: Arkham Knight, Street Fighter V, Fallout 4 and Destiny.