More hiring mistakes are made in the first 30 minutes of a job interview than at any other time. When interviewers meet candidates they like, they maximize the positives and ignore the negatives. When they meet someone they don't like, they reverse the process, seeking out negative information.

Getting past the first 30 minutes without making a yes or no decision is critical to increasing assessment accuracy and preventing most common hiring mistakes. This is harder than it sounds, but here are some ideas that might help.

1. Suspend judgment. Hear all of the evidence, pro and con, before making any decision. In the case of interviewing, wait for at least 30 minutes after the interview starts before concluding whether the person is a possible hire.

2. Be a juror, not a judge. Listen to all of the evidence before reaching a yes or no decision. Once you reach this decision, use any remaining interview time to seek out evidence to prove it's right. To reach a more objective decision, seek out evidence to disprove your decision and balance that information fairly.

3. Divide and conquer. Don’t give anyone on the hiring team a full yes or no vote. Here's a sample of a talent scorecard you from my book The Essential Guide for Hiring & Getting Hired. Use it to assign each interviewer a sub-set of all of the factors predicting success. During a formal debriefing session each interviewer is then required to substantiate his/her ranking on just these factors with evidence. This way the whole team makes the assessment, neutralizing the impact of biased assessments.

4. Be more cynical with people you like. When you like a candidate you naturally go into sales mode, ask softball questions, and ignore or minimize negatives. To overcome this natural tendency, force yourself to ask tougher questions, digging deep into the person's accomplishments that most directly relate to your job opening.

5. Treat people you don't like as consultants. Sometimes candidates are nervous, sometimes they're different from you in appearance or personality, and sometimes they talk with accents you don't like. And sometimes, these are great people. To find the truth, assume they're great, and treat them as expert consultants. After 30 minutes you might discover they are.

6. Ignore fact-less decisions. During the debriefing session, ignore assessments that include these terms: feel, think, like, dislike, bad fit, too soft, too aggressive, anything about personality good or bad, or the term "soft skills." These are all clues that the candidate was interviewed through a biased filter.

7. Don't conduct short interviews; use panels instead. If you want to make the wrong hiring decision, have 5-6 people each spend 30 minutes with the candidate, then add up their yes/no votes. Well-organized panel interviews (60-90 minutes) with 2-3 people each take less time in total, and force objectivity.

8. Conduct phone interviews first. Conduct a 30-minute exploratory phone interview focusing on major accomplishments before meeting in-person. This alone will minimize the impact of first impressions.

By forcing a delay into the hiring decision, and demanding that interviewers justify their assessments with evidence, you’ll avoid the tendency to hire 90-day wonders. These are the people who 90-days later you wonder why they were hired.