Learning by Doing
The reality program The Apprentice has been on the air for seven years, but the concept is centuries old. Apprenticeship was an accepted method of learning a skill. For instance, Leonardo da Vinci apprenticed out at age 14 to a famous artist.

An aspiring entrepreneur might consider the idea to learn about an industry through personal observation and on-the-job training. There are many established apprenticeship programs, but independently finding a veteran business owner willing to teach an assistant is an idea worth serious consideration.

References
http://www.doleta.gov/oa/apprentices.cfm
http://www.apprenticeships.org.uk/Employers/The-benefits.aspx