A professional is a worker required to possess a large body of
knowledge derived from extensive academic study (usually tertiary),
with the training almost always formalized. Professionals are at least
to a degree self-regulating, in that they control the training and
evaluation processes that admit new persons to the field, and in
judging whether the work done by their members is up to standard. This
differs from other kinds of work where regulation (if considered
necessary) is imposed by the state, or where official quality
standards are often lacking. Professions have some historical links to
guilds in these regards.

Professionals usually have autonomy in the workplace—they are expected
to utilize their independent judgement and professional ethics in
carrying out their responsibilities.[4] This holds true even if they
are employees instead of working on their own. Typically a
professional provides a service (in exchange for payment or salary),
in accordance with established protocols for licensing, ethics,
procedures, standards of service and training / certification.

The above definitions were echoed by economist and sociologist Max
Weber, who noted that professions are defined by the power to exclude
and control admission to the profession, as well as by the development
of a particular vocabulary specific to the occupation, and at least
somewhat incomprehensible to outsiders.[citation needed]

Therefore it would be appropriate to state that a 'true' professional
must be proficient in all criteria for the field of work they are
practising professionally in. Criteria include following:

The highest academic qualifications - i.e., university college/
institute
Expert and specialised knowledge in field which one is practising
professionally
Excellent manual/practical & literary skills in relation to
profession
High quality work in (examples): creations, products, services,
presentations, consultancy, primary/other research, administrative,
marketing or other work endeavours
A high standard of professional ethics, behaviour and work activities
while carrying out one's profession (as an employee, self-employed
person, career, enterprise, business, company, or partnership/
associate/colleague, etc.)
Also taking into consideration natural & harnessed talents integrated
& used with qualifications & when doing work in professional capacity.
These talents~skills are just as important in any forms of work be it
paid, unpaid, volunteer, domestic jobs or any other work.

http://en.wikipedia.org/wiki/Professional