An attitude of I-can-make-it-happen, an infectious passion for what one does and a deep belief in one's ability to truly make a difference is what I always like to see in a candidate. I believe it is candidates' confidence that explains what’s there in the resume. However, what is important is to understand the business perspective first.
Once I met a candidate during an interview. After understanding the company's business perspective he asked focused, relevant and probing questions that impressed the interview board. Besides he also substantiated his points with data and instances that has given strong credibility to the 'been there - done that' factor.
People with low ambition communicate their disinterest through their body language such as drooping shoulders, not meeting the eyes while speaking. Years ago I met a candidate who was prospecting a job for a people managerial role. He had a very low voice, low on energy and for every question; I had to make an effort to get answers out. It was really difficult for me to imagine handing over a team to that person. Candidates should understand that interview forum is the entry point to an organization. Their knowledge and confidence is the key to cross that barrier.