I've Been thinking about brainstorming lately. I'm approaching the end of my third adventure, and the avenues of exploration are opening again. I've got a few Ideas kicking around, but it seemed like a good topic to open up for discussion.
I have filled three notebooks with sketches, jokes, and notes over the last 2 years. I've bent my wife's ear with my inane ramblings to the point of breaking. I even have a Facebook group for anyone willing toss Ideas around with me. I don't think anything is created in a vacuum (Let's not bring physics into this, it's a metaphor, or maybe an analogy, let's not bring grammar into this either). I've heard people suggest exercise, coffee shops, adult situations that seemed inappropriate for the conversation at the time.
How do you get the juices flowing? Work out the Kinks? Generate that next spark of genius?

I sacrifice a virgin on the sabbath and pray to the dark one.

Long showers, naps when I can grab them, and travel. I've found the solution to long-standing writer's block on familiar trails and roadways and during vacations. I also frequently have ideas hit in waiting rooms. So, I always make sure I have a pen and notebook with me.

New or favorite shows, movies, or books can spark an idea too. Maybe an interesting character or plot point or even nature of presentation can jumpstart a train of thought.

When I have an idea, especially if it is a jumble or I have trouble getting it in words, I will sometimes seek out a willing (hopefully; I usually feel bad asking) sounding board. It has to be someone familiar with my story/characters who is patient and will give me feedback and hopefully new angles. Just having someone to talk to forces me to organize my thoughts into something less chaotic, and feedback helps me look at entirely different approaches. It's not as easy to find a good sounding board as it sounds. I've found my circle of friends tends to range from the “That sounds great; everything is great” level of useless praise to the super opinionated “Do it my way. No other way. No. This way only.” or “That's bad. I have no advice on fixing it.” My experience has been that online people are WAY better sounding boards than friends, family, and loved ones you see in person. You are super lucky to find one. (I have around three.)

When I have a perfect idea I don't need help with, I go to my “useless praise” people because sometimes, I like to be reminded how awesome I am.

I love the way you think Bruno :)

Like Usedbooks- long showers, books, and movies all spark ideas for me.
Talking them over with friends too! Talking with Pitface, Banes, and Tantz has resulted in heaps of good ideas for me and we'eve all helped each other out with comic ideas pretty much- EACH of us has come away with ideas that we've used in our work from chats we've had after Quackcasts.

Ideas don't need to be well developed either, just a little seed or fun notion is all you need, chatting to others can help grow it.

The notepad app on my phone is the god of brainstorming for me. Whether I'm sat on the toilet having a massive dump, waiting for a taxi or had an epiphany while playing pokemon go, I use that app to record my ideas. often my idea come best when I'm away from my computer, most commonly when I'm out somewhere, whether it's getting exercise or with friends or family.

I find that my ideas start off very abstract. Like a feeling or a mood. I want my next story to be “on the run”. More of a thriller. And very Urban. Back alleys and four story walk ups. But that's it. Now I have to go back and figure out crimes and antagonists and plot stuff. Although another story Idea I've got rolling around started with one image of the crime scene and now I have to work from there. I do most of my thinking in the Shower. It's about the only time I don't have distractions. Sometimes I can zone out at work, but I tend to end up posting stuff like this on the internet instead ;)

i seep into something else. make something else for awhile. take a walk, listen to music.