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.
Avoid Cliches. There are a few standard reasons why people become doctors, and so it is very easy to fall into cliched expressions and ideas. Though it's fine to express a commonly_held notion, try to find a personal way to express it. For example, rather than write "I want to be a doctor because I want to help people," discuss the ways that you have shown your generosity and kindheartedness in the past; bring specific examples__such as your volunteer experiences__so as to avoid a direct (and possibly cliched) declaration of your point. Sometimes cliches are unavoidable; just make sure your essay isn't full of them.