If you have someone in your area who is a racer, learning from them is the best way. I am lucky in that where I live, I have a large group of 'cross racers from whom to learn. Once you learn the basic moves, it takes A LOT of practice to get it right (I'm still working on that 4 years later!).
A clinic is also a GREAT place to learn these skills - see if your local shop puts one on or knows of one in the area.
There are some videos you could watch, but I think having the first hand experience is the best.