Your medical school personal statement needs to sell. Every single word has to sell your reader and answer the question: "Is it worth my time to read one more word of this essay?" To be persuasive is to sell your reader on your next sentence, your next paragraph, your next idea of your medical school essay.
The first place that you should look for sample personal statements is on the website of the school in which you are attempting to get into. If you can find samples of the admission essays of others who have already been accepted into the school then you can really begin to dig deep and find out what will be expected of you. Depending on the school in which you are trying to gain entry to, finding these samples can be easy or darn near impossible. When the latter happens you can always turn to the internet for help. Just as with anything else these days, the internet has an unbelievable amount of websites with samples of various types of admission essays. You can begin by conducting a Google, Yahoo, or Bing search on 'personal statement examples' and then begin to look at the different results that come up.