I keep a list of ideas going on my smartphone, this way when a topic or video idea hits, I write it down. There isn’t any “Special place” this happens, unlike some of the other responses.
Also I find breaking out the camera around entertaining friends is a fun way to capture some interesting Vlog-Type videos.
Keep doing what you’re doing, the more videos you make, the more ideas you’ll come up with, it’s like a weird creative cycle.