The following book is an excellent introduction to training.  It is
illustrated with good photos.  I do not recall if they use a clicker or not
but it should work since my ferrets are trained to come for treats when
they hear small pieces of dog biscuits shaken in a jar or me making a noise
with my tongue.
 
Gerry Bucsis and Barbara Somerville. Training Your Pet Ferret. Barron's
Educational Series, Inc., October 1997, ISBN # 0-7641-0093-9
 
Lorraine Tremblay & Marc Lavergne
Webmistress of Mustela Canada
Webmestre de Mustela Francia
http://www.storm.ca/~ferret
[Posted in FML issue 2451]