I believe that in order to identify a high calibre candidate you need to be one yourself. There's no value in recruitment based on key words you do not understand.
To answer your question in five points:
1) I would look for recruiters that have relevant working experience in the domain I am interested in, in order to fully understand my overall domain needs. This goes both ways as I might also need some education related to latest recruitment trends in my domain. I look forward and always appreciate that kind of feedback. It builds trust for a long term commitment.
2) I would look for recruiters that are on top of their game when it comes with being agile and staying ahead. I look for people that understand the differences in generations. How millennials are different from baby-boomers for example and how to approach them in a customized way, because of the previous understanding.
3) I would look for recruiters that are curious and ask questions regarding the company culture before they go on technical JD details. Hiring the right people is very important, not just the people that can do the job. A good recruiter should understand the culture and project it back to me as confirmation. Further more the recruiter should present to me a method of identifying candidate's personal values and match them accurately against the company culture.
4) A good recruiter should also accurately question, identify and match the soft skills/capabilities of the team and of the candidate. Aspects like: social, communication, attitude are very important to the future long term integration.
5) A good recruiter's relevant technical domain knowledge and experience should also be used to properly identify, understand and match all the technical aspects of the JD.