Sappi Paper has a great educational series called  The Standard. The most recent version, The Standard 4, is all about Scoring and Folding. The printed book is a great reference detailing the basic styles of folding and scoring with a great section of do’s and dont’s
Check out this great video on the basics of folding.
http://youtu.be/kIXAbPZkTKk
For more information on Sappi paper visit their website  http://www.na.sappi.com/home