AutoCad :: Sharing Files Between Computers (no Server)

What is the best way to share dwg files so taht stuff doesnt get messed up? The designer says taht civil3D now uses something call dat references, this is new to me since ive been out the game for a couple years, how do you send those files? are they within the drawing?

Basically here is my problem, the designer does all the design, plan and profile, than he sends to me to put in the notes for the plan views, not knowing if when I save the file it will mess up his profile, he jsut copy pasted the notes I put in into his original file, as oppose to jsut overriding it. So in essence we are doing double work..

another thing, he sent me the proposed base file, and when I got it I got big text saying that there is a broken reference. I went ahead and made some changes and sent back to him thinking it would go away cause it will find the reference on his computer, but it didnt. And than he said that the drawing I sent him didnt have any settings under "toolspace" like his original did.