I have heard that Google tries to control for this by having one panel of people as the Interviewers (i.e. actually meet/talk to the Interviewee) who then write-up their respective reports. This set of reports are then submitted to another panel (who have NOT met/talked to the Interviewee) who then have to make a hiring decision based solely on the reports.
At that point the panel makes the call based on a biased report and it thinks the decision is unbiased which is not true.
As an example no words which might create a impression but sticking to facts. The inference is left to the second panel. For example instead of saying the candidate thought hard about the given problem say something like the candidate tried out 3 different solutions to the problem over the interview time period. The first panel are merely conveyors of Data; so their reports have to be detailed and to the point.
For example if I'm interviewing someone for a technical position and they're very attractive or even dressed/groomed excessively I'm making an effort to not hold that against them. I'm aware that I have a bias on this so I'm actively trying to have a balanced perspective during the interview.