There is a lot to the definition of a professional. There are many questions here asking how to identify components of what is essentially a professional programmer - how do you identify or communicate expertise, specialization, high quality work, excellent skills in relation to the profession.

I am specifically looking for methods to communicate a specific component, and I quote from wikipedia:

A high standard of professional ethics, behavior and work activities while carrying out one's profession (as an employee, self-employed person, career, enterprise, business, company, or partnership/associate/colleague, etc.). The professional owes a higher duty to a client, often a privilege of confidentiality, as well as a duty not to abandon the client just because he or she may not be able to pay or remunerate the professional. Often the professional is required to put the interest of the client ahead of his own interests.

How can I most efficiently communicate my professionalism, in the spirit of the quote above, to current and potential clients and employers?