Many years ago I stopped telling those people I worked with, for whom I was the designated leader organizationally, that I had an open door policy.
Intuitively, I felt inviting people to my office, to share their thoughts and ideas openly could send a subtle message that I was open to feedback,sugestions etc, as long as they were made in my seat of power.
My office was not a neutral place. For me, this was a place of power. Seeking open and candid thoughts from others is not only impacted by your body language and clear indications of receptivity.
Encouraging others to talk to you in places they are comfortable will result in much more open information exchanges. This could be at their office, desk or workstation. In a break room or a coffee shop.
More often then not I went to my subordinate for a discussion (rather than inviting them to me) and I consistently found these to be more comfortable and relaxed discussions.
Seeking Input
What others think, open collaberation and sharing ideas is an extremely effective way to develop high performing teams. A top notch team of which you are a participant in, not a driver or solely direction setter.
Keep in mind the time and place of a discussion is often as important as the topic and discussion facilitation to ensure an open exchange of ideas.
Spend time with your teams. Show them the openess you have toward frequent and honest communication. Don’t expect them to come to you. You are far more likely to get the feedback you need by actively seeking it.