When hiring externally, what specific activities has your organization successfully used to ensure that candidates will fit with your culture?

I've found the most effective test of this is scenario-based questions at interview, reflecting likely situations and focused on uncovering a candidate's thinking and approach rather than 'right' answers. The biggest problem in making it scale-able has been the level of questioning and observing skills, which doesn't always exist within a team. However, when the fit within the team is right, the wider cultural issues have rarely been a problem.

STAR Method.

KSA Assessment.

Depending on the position, tools include: 1. Open fora for on-site interviewees;1. Behavioral interview questions/scenarios;3. Well developed reference check questions etc.

Personal interview is the best in the selection of the right person that depend on the numbers of questions and hold the interview and how to study the behavior and capabilities of the candidate and his skills and experience and personal knowledge

Headhunters and well prepared interview including specific questionnaire.

Personal interview with well prepared questionnaire, behavioral test, testing of decision making ability can help a lot in this matter.

At first i need the candidates that will fit to my job , and the questions of my questionnaire,and  behavioral test can ensure  the candidates will be fit to our culture

As my  work experience, We are looking education,experience and then interview questionnaire process according to mention post. When we are satisfied to him then hired.

First, we look for someone who's matching the position and then by different tests we find out how close the candidate to requirements

Position analysis and needs analysis and CV and compared with the vision and culture of the organization

If you haven't assessed your own work culture first, you have no real tool to use to evaluate the candidate.  Topics to discuss include work style (Authoritarian?  Collaborative?), Problem-solving approach (team-based or individual?), work environment (relaxed or formal) and level of pressure (meetings and deadlines or independent thought?)  What about rewards?  Are they individually based or based on the overall performance of the unit?  

Once you have really assessed your own culture and what you want to develop, you can assess what affect the candidate will have on the goals tomake that culture a reality.  It doesnt matter how much someone knows if they are not the right fit for the organization.  i am a fan of certain psychological profile exams for this purpose and have found them to be quite helpful, particularly at the senior level.  Expensive, but very much worth the money.  Find someone who knows what they are doing to administer it though.  You can try a free version to get a feel for it at http://www.16personalities.com/free-personality-test, but i would get a person who kows what they are doing to evaluate the results.