Not just claim to be a "professional" but earns a title by successfully completing the rigorous PPI accreditation process. We welcome worldwide photographers to apply for our accreditation and succeed in this competitive business. The PPI provides the following to help you become more professional:
As an International Accredited Photographer of the PPI you are required to continue your growth and personal development as a photographer. There are three levels of PPI accreditations.
You could also check out some of the example portfolios and useful information from here.