One of the most important things to understand and get clear on when thinking about your calling and your vision for your life is your values - what truly matters to you and how you want to live your life. This is especially important when searching for a new opportunity. The culture of the organization that you work with has to represent (or, minimally, be accepting of) your values in order for you to be truly fulfilled.
While most people out there talk about values elicitation in a positive frame ("Think about those things that matter to you" type stuff), one of the tricks I've found is that choosing a negative frame can help you understand some of your values that you hadn't thought of before.
My favorite way of asking it: "What, if your company or boss did it, would be a complete deal-breaker for you? What would make you completely disengage?"
You may find that you get answers that you wouldn't have thought of otherwise. I know that I did. While I hadn't originally thought of it, one of the things that is a fundamental value for me is the culture of taking ideas for their value, rather than by position or other external factor. That is, that everyone's ideas have equal merit based on the idea, not based on who the speaker is or what their role is.
It's a value that I've always held implicitly and it has been a part of all of the truly fulfilling cultures I've been a part of. But I wouldn't have thought to call it out explicitly unless I looked at what I would notice when that isn't present in an environment I'm in, and how I react.
What are the dealbreakers for you? What could your company (or prospective company) do that would make you not want to work for them any more?