Moving in doubles

I never really had much experience in doubles despite being part of the school team back in primary school. But then again back then all you had to do was stand there and hit back (though I think it's evolved a lot more since then).

So I had a nice conversation with a nice man today who told me the basic rule of doubles movement. Once again, it all comes down to footwork and coordination, and I wouldn't have it any less.

"If your partner backs off, cover the empty space in front of him."

Sounds easy enough, but wait till I attempt to put it into action...