One of the easiest ways to identify the NAICS or SIC for an industry is to look up a company in that industry using one of the business databases, e.g., Nexis Uni or Mergent Intellect. The descriptive information about the company almost always includes a listing of the industry or industries in which the company is engaged.
NOTE: NAICS replaced SIC in 1997, but some databases still include SIC codes in the listings.