Here are a few tips about how not to fail at interviewing people:

• Set expectations right up front. Don't blindside people with a ten person panel interview when they think they're just coming in to talk with a hiring manager or someone in HR. Yes, we all understand you read something somewhere that it's important to see how people react under pressure situations like that. Here's a hint - while they're outwardly smiling and shaking hands, they are plotting the deaths of everyone involved in the interview.
• Be prepared. For every complaint that I've seen from the hiring side of the table about unprepared candidates, I've seen / heard an equal number from the candidate's side as well. Have their resume. Please have read their resume. Know who they are, what their skills are, and the job(s) for which you're specifically interviewing them.
• Loose lips sink ships...and careers. It's great that you've held an open day
  
  call for talent. It's nice that you're trying to simplify your own process by creating a single email to let all of the candidates moving on to the next round of interviews. How about you use the BCC: field instead of the CC: field so that some of those candidates don't start getting questions about if they're leaving their current job, or why they're leaving their current job, or hey, that's cool, someone forwarded it to that person's current boss because they're a friend...
• Lay out the process. Is this the only interview? Will there be one more? Two more? Five more? Knowing that in advance will help people figure out if this is for them or not. And again, we get it - "culture" is important to you...but people's time is important to them as well. Four interviews to get down to group that still has at least three more interviews to go...and they didn't know that ahead of time? Guess who's dead to a lot of people and gets a bad rep around town for wasting huge amounts of people's time? You are.
• Be positive. You know how you're always telling us to tell candidates to be positive? Guess what, Skippy? If you're in a rotten mood and/or having a bad day at work, and this is the candidate's only exposure to the company...well, culture matters on the other side of the interviewing table too.

Always trust your instincts.

Ref Gordon Thredgold