When "something doesn't feel right", I go to the next stage of cautiousness. When I KNOW something isn't right, it's a problem.

I'm not sure if that answers your question, but it is a very broad topic. I trust my gut and subconcious, and if they think something is fishy, I listen. I think the best answer that I can give is a movie quote: "If there is a doubt, there is no doubt."