A good personal statement depends on the subject you’re applying for, but here are a few tips:
1. Make sure that about most of the statement is about your pursuits relevant to the course (I suggest around ¾). Tutors only truly care about your intellectual ability and interests; non-relevant extra-curriculars only really serve to supplement this and show you can manage your time.
2. Don’t just list books and extra-curriculars, but show what you’ve done/read is relevant:
E.g. Instead of saying “I did debating and public speaking” say “Debating and public speaking have helped me with communication…”
Similarly, don’t say “I enjoyed such and such a book”, say “from such and such a book I have decided that…..”. This shows you’ve taken something on-board from your reading, and also provides a stimulus for an interview question.
3. Show off. No-one else will do it for you, and an Oxbridge applications isn’t the time for being modest. Word your achievements in the best possible way (without lying, obviously). Do you play netball for your school? That’s great, but why not highlight your best achievements on that team?: “I captained my netball team which are currently District Champions” is better than “I play netball in my spare time”.
4. Read things that excite you and which you can be enthusiastic about. There aren’t necessarily books you have to have read. E.g. for my PPE application, I talked about a couple of Development Economics books I had read. This meant I could be more enthusiastic about my reading, and meant I stood out from applicants who just talked about “Freakonomics” (the classic book every Economics applicant reads)
Last but not least:
5. Make sure your Personal Statement is crystal clear to read. Include lots of paragraphing, and avoid long-winded sentences. A tired professor will be reading your PS after sifting through piles of other Personal Statements. Make his job easy and chances are he or she will be much more likely to accept you.