What does it mean to lead with your hips?
It refers to making the front hip lead the early part of the stride. This would be as opposed to leading with the front foot which means the front leg has opened up early.
XV will probably come along with another great picture but the idea is to go through your stride with the front hip leading the way. Keep the head and shoulders slightly behind the front hip into foot plant as this helps keep the front leg and foot closed - allowing the front foot and leg to open early will have the effect of opening the hips early and things quickly go downhill from there.
The opposite of leading with your lead leg (knee, foot) towards home. Think of your your back pocket going towards the catcher as your hips lead forward.
This is something my son that is 11 has been working on for the last couple of months. He has made great strides with it and it has also helped with better hip/shoulder seperation.
We started out by working on 2 thoughts, knee to belly button and then lead with the hip.