My big picture advice on the Personal Narratives:
1. Read the directions and answer the question that is being asked. Sounds simple, but people have a tendency to go off-topic. The Personal Narratives are a chance for you to show the QEP how awesome you are. Don't throw that chance away by answering a leadership question with an experience that's more appropriate for an intellectual skills question.
2. It's a narrative, so tell a story.
3. Be specific. Don't be big picture; get into the details of your narrative. 1300 characters per Personal Narrative is about 200 words or so. Make them count.
4. Use a variety of experiences. Don't show how you fulfill all 13 Dimensions by detailing a single experience that you just re-write for the five Personal Narratives.
5. Use your best stories (no matter how old a story is).
6. Get your writing done early, at least a couple of days before the deadline. This will give you some time away from your writing so you can self-edit more effectively. And you will need to edit.
7. Think very hard about the cone you selected and what life experiences you have had that match the work/responsibilities of that cone. If you've picked the Consular cone, don't demonstrate a bunch of experiences that are more suitable for Public Diplomacy.
8. Think about the structure of your answer. I'm partial to a 3 paragraph format: first paragraph for the set-up (what the problem/challenge/whatever was), one paragraph for the action/solution (daring, dashing FSOWannabe to save the day) and one paragraph on the conclusion or result (peace and harmony/free ice cream throughout the land).
Disclaimer: These are my suggestions. I have no idea if they "work" or not, and I've only gotten through the QEP stage once.
Additional disclaimer: corrected number of essays referred to above (there were only 5 the last time I answered the PNQ's).