If you are going to be one of the interviewers for an engineering candidate, it's best to have a solid plan in advance for your interview. You can use this general outline and customize it for the questions you want to ask and your goals for the interview. Encourage your colleagues to use a similar outline or provide one when training interviewers.
It's common among engineers to say that the only real criteria for hiring someone is that they're "smart and get things done." Does a candidate really understand the difficult technical concepts involved in engineering and do they have the critical thinking skills necessary to solve difficult problems? Do they take initiative in accomplishing goals? If it helps you to think of the interviewee in terms of "smart and gets things done", definitely use that criteria to help frame your questions and your ultimate evaluation of potential hires.