The best candidates out there are the ones that not only allow you to interview them, but they in turn interview you. They typically reached out to you first regardless of current job openings or not. They have great follow up and don't just send a resume for review. They go the extra step and call HR or travel to the office and come in to speak with someone. They have initiative.
They don't want to just choose a job with a company because they have values and understand what it takes to be successful. They want to make sure that your company will help support them in achieving the goals they have in mind both personally and professionally.
When having an interview with a candidate, don't sugar coat the challenges your organization faces. Be open and honest. Describe what the issues and problems and how it could be a challenge for the candidate. Ask him or her how they feel about those challenges.
Make sure to take note of their reaction(s) and what they say. This will indicate whether they are up for the challenge, feel they can contribute or maybe that they're about concerned.
If the candidates answers are broad and rehearsed then they didn't research the company, the industry or maybe even the position. Look for the real answers and reactions.