What is the reader looking for?

I think that in the nature of today’s society, this question is one asked frequently by students - if not by anyone in a competitive ‘market’. This question is applicable to not only the matter of writing a Personal Statement, but also to (GCSE and A Level) examinations. Knowing what the University/marker/employer wants is of utmost importance.
My advice to a student asking this question would be to capitalise on their assets. Any relevant experience or personality traits that present you as being absolutely capable are necessary. It is important to consider the competition that the student is up against, but to remain true to themselves and be honest with the way they present themselves. In this sense, authenticity and a little embellishment of oneself is, often, key.