Games : Minecraft piston door is only shut when lever is on, but how do I turn it off with another lever?

This is a frequent problem I've been having with the designs of some doors. Basically, the door, to be shut must have its redstone to be powered by a lever. So when I want to enter my house I must simply turn the lever off, turning the redstone circuit off, but I'm not able to open and close it from the inside of my by rerouting the redstone? I'm really confused can anyone help me out?