As an Independent Professional, you will continue to develop yourself. There are always new changes in your field and you need to keep up to date to provide high quality services. For example, you can take training courses. Where can you find a suitable training?
A legal consultant who takes a creative writing course will probably never apply it to his work. Pick a training that is relevant to your work and target audience. There are several providers and each has its own specialization. Of course, a training should be of high quality. Therefore, always read the brochure or information page of the training you want to take. It will tell you how the training goes, what subjects you will study and how the exams are taken. Also ask for experiences of other ZP'ers.
Many organizations offer training and the market is expanding. Even LinkedIn, through an acquisition of Lynda, will soon be offering online video courses. If you get a certificate, it will automatically appear on your LinkedIn page. There are already a number of organizations you can go to. For example, the LOI offers a starter course for ZP'ers, and at ZP Academy you will find a wide range of courses.