You're ready to write. It's happening. You sit down in front of a blank page... Now what?
I like to see personal statements as opportunities to put the "why" behind everything you discuss in your resume. Often, the essays discuss challenges students have overcome, but careful -- "trauma dump" essays that don't relate to your current achievements may not be compelling to application reviewers.
If there is a specific story that jumps out to you, go with that. Otherwise, here is the starting point I usually use:
First, think about the message you want to get across. If this is a program-specific essay, what is the award for? Are you trying to showcase your penchant for community service? Your commitment to research? Your love of dogs (there are scholarships out there for pet-lovers!)?
Next, consider what brought you to that field. Was there a specific moment that made you realize how much you adore one of your passions? How were you introduced to this field? Why are you passionate about it?
Pick out a few stories to include and tell them in a timeline, tying each into the next one.
For your key personal statement (and any longer essays), I would recommend having a strong introduction and conclusion. These are great places to really interject some of your personality, creativity, and humor!