Every IT professional can spot a job description that HR has touched -- great candidates turn down your firm at this stage, long before they ever show up in any statistic. You are losing potential employees, the best potential employees, before you ever find out that they were giving you a moment of their time.
You may also accidentally turn away candidates who would happily have accepted a position with your firm but were misled into believing that they were not qualified for a position due to nothing more than an incorrect, often impossible, job description.
It is important, too, to have a generally well laid out and efficient process to move from one interviewing stage to another and to do so, from end to end, in a relatively short period of time. I myself have had poorly planned interviewing processes that stretched for longer than six months. In these cases the people involved will often change positions, or even companies, during the process. The same stages might get repeated over and over with the interviewing company not remembering the candidate or what had been said and determined in earlier interviews.
If an interviewing process spans more than about a week the process is too long and the stages are too disconnected. Decisions should also come in a timely manner, not weeks after an interview has taken place.
The interview process should be designed around the desired candidate traits. If you want to hire someone to just hit the ground running and have no long term viability, focus purely on tech skills. If you want someone to be a part of the team, focus on personality and just make sure that they can learn the tech skills.
Communications between interviewers and stages is important. An interviewee will not be impressed if asked the same question multiple time, especially not if asked by the same person. This is far more common than interviewers may realize.
Put yourself into the shoes of your candidates. Think about how theyll see your company when they interview with you. Will they see an organization that treats them with respect and professionalism? Will they see you as prepared and highly skilled? Will they see processes that encourage the kind of people that they want to work with to join your firm? Or will they see that your company thinks that hiring good people is not a priority?
Interviewing processes do not need to be exceptionally formal or rigid. Alternative approaches can work wonders and can tell a candidate much about your company. But make sure that any process that you implement reflects positively on your firm and is not turning away the candidates that you might wish to hire.
No matter how much you imagine that candidates should be beating down your doors to come work for you -- those candidates don't know that. Until you convince them otherwise, you are just another unlikely job prospect to them in an endless sea of job listings -- unlikely that theyll get an offer and unlikely that theyll accept one if received.