Personal statements involve cramming your achievements, hobbies and personality in a mere 4000 characters. At this nerve wracking time it is most likely very difficult to see what you should include or not include, yet perhaps these tips could help you decide.
The Oxford model was stressed to me as I applied for university to focus mainly on personal achievements and flair for your subjects, thus to ignore your individual hobbies and eccentricities. However, imagine an admissions tutor is trawling through 2000 applications, perhaps your unique hobby could attract their attention, especially if you have gained recognition or competed in that field.
One of the most important things in a personal statement is evidence of passion for the subject you are wishing to study - not just enthusiasm for the profession it leads to. Universities are very interested in you contributing to their student body and what new ideas you can bring to them. Simply treating university as a stepping stone and not acting like university is even for you will get you nowhere. To show your interest a good idea is to read around your subjects and mention books you have read. However, do actually read them. Don't fall into the trap of shoving books down and getting caught out at interview!
If you have a part-time job you feel is worth mentioning, feel free to. However, do not get caught up wasting too many characters on this, especially if you are unable to validate how it has spurred on your interest in your field.
Another thing to avoid is humour, clichés and over-used quotes. It is very hard to tell how your words could come across, so unless you are dead certain your pun will receive a chuckle, it is best to keep it out. Clichés such as "my passion for this subject has started since I was little" are seen by every university, every year. Originality is your secret weapon, don't waste it!
So, in summary universities want to see you in your shiniest form, essentially surrounded by academic accolades and own quirks, encapsulated on a piece of paper. Not too hard, is it?