Discuss the nature of capital structure and how capital structure impacts WACC.

You are in a meeting and just explained how WACC is used to discount cash flows in the valuation process of a company. So$,$ two ways you can increase the value of a company either increase Free Cash Flow or decrease WACC.

The CFO says that they can increase corporate value without the fuss of increasing revenue or decreasing costs, they just need to lower WACC and they can do this by changing the capital structure.

Really? Tell me more, if it is so easy. What is this and how can they get it done?