Around 80% of your statement should relate to academic studies, work experience and how these contribute to your interest in the course and potential to do well. The rest can be used to cover extra-curricular activities.
When writing a personal statement for university it's best to include specific examples of activities and achievements that make you suitable for the course, and explanations of how these will help you to succeed. It's also preferable to select a few of the most relevant examples with details, rather than a long list of your attributes and interests.
Your skills, achievements and experience should be explained in terms of relevance to your course. For example, if you are applying for a course in business with entrepreneurship, you should mention any work experience you gained in industry or any entrepreneurship competitions you entered.
Admissions tutors will be looking for evidence of your interest in a subject. If you are applying to study journalism, for example, you could mention your own media habits and preferences or your experience of blogging.
After every new point you make, ask yourself if the information you have given supports your application. It's better to pick a couple of your activities – the more recent the better – and discuss how they have contributed to your skills. For example, what did being captain of your netball team help you develop? Your organisational skills or time management, perhaps?
Demonstrate your knowledge and enthusiasm of the subject area, what you will take from the course, and where you see it leading in your academic or professional life after university.
Don’t waste words explaining why you haven’t done something. Focus on the positives.