This one is a trap since many people don't answer this properly. You have to describe something that would obviously be a weakness to them (like no administrative experience, minimal employment history, etc) and discuss it, but be sure to put their mind at ease about it. If you were let go from a job and they know about it, bring it up. Now is your chance to explain to them how you have grown from it and/or it will not affect your position here. Turn this "negativity" into something positive so there is little to nothing for them to worry about in regards to hiring you.