A good PS doesn't have to be about a monumental life altering moment, although many good ones are. All you really want to convey is who you are and give reasons why you would make an excellent law school candidate. Treat it as if you were having a beer for 10 minutes with the reader, what would you like them to know?
Just about everyone has at least one good story to tell, even if you don't know it. The problem is that you know yourself too well. What seems mundane and ordinary to you is probably extraordinary -- you just don't know it. Things to consider in your PS:
1. The most important thing is to keep it personal! If it is personal to you, you will naturally show more passion in your writing.
2. The why do you want to go to law school essay: What do you want to be when you grow up? It is best not to berate lawyers with what you know about the law, but to explain how it fits in your background and/or your future. Why is the law personal to you?
3. What was a turning point in your life? It could be mundane. I read a PS where someone wrote about arguing with a contractor about the meaning of the word 'install' as applied to their new kitchen cabinets. I read one about someone who argued about being the middle child and its relation to a lack of justice.
4. What are your interests and abilities? Write about a camping trip you had that was memorable, or your experience in hockey, or the time your band performed in front of 30 people.
5. Write about your lawyerly traits that you discovered in your job.
Things to avoid:
1. Don't be general.
2. Don't write "and this is why I want to go to X" unless you have reasons which are personal to that school.
3. Don't sound like a jerk. (ie being wordy or condescending). Be clear and concise. Try to be near two pages double spaced. They will only spend a few minutes reading it, it is in your best interest to make them want to keep reading.
4. Don't start with a quote.
5. Don't tell lawyers about the law -- They know more about it than you do and when you are wrong they will not have a high opinion of you.
6. Don't have a sad theme running through. You don't want pity, you want to show why you are a strong law school candidate.
6b. Don't end it with "The end". Not sure if anyone does, but I would avoid it