In general, previous work-related skill, knowledge, or experience is required for these occupations.  For example, an electrician must have completed three or four years of apprenticeship or several years of vocational training and often must have passed a licensing exam in order to perform the job. 

Most of these occupations require training in vocational schools, on-the-job experience and informal training with experienced workers.  These occupations usually involve using communication and organizational skills to coordinate, supervise, manage or train others to accomplish goals.