How do you brainstorm with yourself?

I feel one of the biggest productivity blockers for me is getting stuck. This tends to happen even though I'm very conscious about taking small breaks and not pounding too long on a problem if I don't get forward.

What will happen is that I'll flick around unsure about what is the next step, and not realizing that I'm stuck. Many times I might also miss some obvious easy step I could take to get one step forward, just because I'm not yet aware that I'm stuck, and haven't been actively seeking a solution.

Thus, I was wondering, what are your best advice for:

1. Realize as soon as possible that you are stuck and need to stop to seek out another approach

2. Brainstorming with yourself - How do you get to think about those kind of obvious things that you might miss just because you are too buried in your current work?