There are two main ways to gain work experience:
The route you adopt will depend on the type of work experience you are looking for. Some industries such as engineering, IT, finance and business management are more likely to advertise paid vacancies.
Positions in other fields including media, marketing, journalism, culture, sports and psychology are less likely to actively advertise. If you are looking for work experience in these areas you will need to spend more time finding out about organisations in the field and making speculative approaches to them.
More formal types of work experience like year placements and summer internships are also more likely to be advertised than short term and part time positions in professional settings.