All PSs will have an introduction in some form. This needs to start in an interesting way, to draw the reader in straight away. Remember that admissions tutors will read hundreds, if not thousands of them! 'I am applying to study LLB Law' is (a) a waste of characters, as the admissions tutors will be from the law department and (b) a very boring way to start a PS. Avoid cliches such as 'I have always been interested in' - technically that can't be true, as it would have not been the case as a baby! Also, it is best advised not to use quotes in your PS - it is meant to be personal to you, so the admissions tutors want to know what YOU think, not what someone else does. It is also advisable to avoid references to other subjects. Statements which open using metaphors relating to the classical world or Shakespeare do not appear to be clearly for law from the opening sentence.
Use the introduction to possibly talk about HOW you got interested in law (although don't say 'studying AS Law has made me want to study this subject further,' as it will bring up the question 'well why did you choose to study AS?'. Don't talk about wanting to be a lawyer/solicitor/barrister. An LLB is not a vocational qualification: further study is required to qualify, and a number of law graduates do not go onto qualify as either. Mention an area or two and say WHY it/they interest you, albeit briefly. You can go into more detail in the subsequent paragraphs. Whatever you choose to include in this paragraph, it should have a strong, attention-grabbing opening sentence without sounding too clichéd. It's probably best not to use a quotation for this purpose as it can make you sound pretentious.
Academic content should take up approximately 2/3 of your PS. It can be split into two: college academics (A Levels etc) and academic interests/activities outside of your formal education. The former is obviously more interesting, as it shows more motivation to know more about the subject you are wanting to spend 3+ years (if you include a relevant postgraduate course) studying. However, you may not want to separate them that crudely - for example, covering something at A Level may have enthused you to discover more about that subject, so put it together.
This is not the place to list your A Levels and what you've done in them. It is also not the place to try and link everything to law, no matter how tenuous the link. Try and avoid saying 'Studying English literature has improved my essay writing skills and helped me construct concise arguments/Mathematics has helped with my data analysis skills'. These will be pretty self-evident and a waste of characters. Instead, talk about what in your A Levels (related to law) has interested you and why.
The second part would be far more interesting. This can come in a variety of forms: reading undergraduate level text books/reading academic journals (including those aimed at college students). When talking about these things, make sure to say WHY you found it interesting, and offer your own opinion/evaluation of what you read. You will have to get used to debating/backing up ideas with evidence, so it's important to show the admissions tutors that you will be a good candidate/student for the course. When discussing research you have done, it is important that it is relevant research. Mentioning research on the judicial system of another country is not particularly relevant or useful.
Generally, this will come in the form of work experience in a solicitors firm, or observing in court rooms. It can be difficult to mention this without mentioning too much about 'being a lawyer', so focus on the academic side of law. Relate everything you do talk about in this section, to the background/theory/concept in law that it relates to, and explain why you found it interesting.
This section is for anything that is not specifically related to your interest in law. This part should be short, a maximum of 1/3 of your PS. It can include things from school/college as well as in your free time (including a part time job). For school/college, you may want to talk about peer mentoring, prefects. Remember to keep your sentences short and snappy. If they're long, people get bored and stop reading. Cut out all unnecessary words. Don't start your sentences with verbs unless absolutely necessary (e.g. “Being a prefect” is too informal). Say what you did/do, then what you learned from it, and sometimes explain why that is useful, but not at the expense of it being interesting. Don't repeat things you learned- you only need to demonstrate characteristics once each throughout the statement. You don’t need 3 examples of how you can handle responsibility! Other characteristics you can talk about are team work, communications skills, leadership, confidence, etc. Don’t worry if you don’t include them all. If it is just going to sound fake and boring, it’s probably better not to bother. You do not need to relate everything to law - you are allowed to have a break from it, even at university!
As for your interests outside of roles of responsibility, keep it very brief. Sport and musical interests are generally good ones to include and just briefly say why you enjoy it. Less important are things like 'I enjoy going down the pub with my friends/shopping/going to the cinema' etc. As long as you have SOMETHING written about your extra-curricular activities (if just to show you exist outside of college), it doesn't matter how many. Quality is better than quantity, and you want this section to be brief, so there is no point in listing a load of activities. Think about how they've helped you.
If you are deferring entry, it would also be useful to include any gap year plans and say why you are doing that.
However, if you are an international student, it is not necessary to mention why you want to study in the UK.
Your final paragraph should conclude why you are a good candidate and why you want to study law. Although you should be confident that you are a good candidate, it is important not to sound arrogant (e.g. 'I am the ideal candidate to study law'), as it's very off-putting. You shouldn't include any new information in the conclusion, except possibly career plans. Don't worry if you don't have any, you don't have to mention career plans at all. Don't refer to the university directly ('your university') as this comes across as very insincere considering you're applying to 4 or 5 universities.