To me, the very worst, most dangerous thing a parent can do - even without realizing it (and I admit occasional guilt) - is to simply not listen to what your child is saying to you. To tune them out as white noise that is competing with what you would rather pay attention to. When I realized that I was doing this, I was shocked and disgusted with myself, because that's what my parents did to me, when I was young. After realizing this terrible habit, I adjusted. Now, regardless how minor, ridiculous, irrelevant, or whimsical, I listen to everything my children say with undivided attention.
The thing that really snapped me out of that rut was the fact that my daughters have lost 3 of their friends, this year alone, to suicide. The chief complaint among those three, before they left? They felt neglected by their parents. Just unwanted baggage. I never want my children to feel that. It is unavoidable that a parent will make their child feel that way, simply by denying them something they really, really think they need. But, that's not the same thing... and they realize that. But, when parents dismiss their children with a nod, a "mm hmm", and a wave of the hand, how else are they to feel? So, I made it a point to be attentive. It can be difficult, especially when the conversion consists of 12 1/2 minutes of "My Little Pony" fan fiction... but it's important to her. Because of that, I give her that ear to show that she's important to me.