How to free a Interface?

i'm new with this thing named interface and DirectX. I'm hooking a DirectX Interface from a certain game and i'm using the DirectX to Draw My Own stuff,like textures and Fonts. My problem are that: When the program call the Hooked Reset Function of the Device,i need to clear all my things from the memory,the Com Interfaces.If i not clear,after the Reset event are called,the Game just try to create a new surface calling d3dDierctx9Create but its fail and just make a error and close the game.

I think that i just need to clear all the things before the Reset Event,its is explained on Msdn.