Avoiding platitudes will go a long way. Here's a tangentially-related example: Peter Thiel recently wrote (in Zero to One) that he decided not to invest in anyone who wore a suit.

Imagine if your hiring committee had a similar platitude. Is it illegal? Arguably no. Is it going to narrow candidates down based on any criteria that actually matters to the job? Probably not. I think catching yourself when you're tempted to use these kinds of heuristics is the key. Ask yourself, "are there any direct causal links between performance and the metric I'm measuring?" If not, you might not want to use that metric to make decisions.

[1] http://www.businessinsider.com/peter-thiel-hates-suits-2014-...