Depending on what it is, it's usually just in my head and then a debate with others.
If an idea requires the participation of several people, I prefer to stop because I know from experience that I can rely on and trust only a few people, but they're already obsessed with the realization of their ideas :)
On the other hand, if I propose an idea that I can't implement myself, others usually don't understand.
So, I realize what I can process on my own through trial and error, and then I remove the mistakes.
But if I'm in a group, I like to get one piece of an activity that is then part of the group. I don't like it when it comes to an agreed-upon realization that somebody else wants to be clever.
To make ideas a reality is the most complex process, I think.