The key to a personal narrative is to choose a clear idea that you can develop. It needs to be something you remember well, and something you can discuss in detail.
[The] personal essay is noted for “its friendly, conversational tone, its drive toward candor and confession, and its often quirky first-person voice. (enotes)
Then you need to develop the essay. Organization is just as important in a personal essay as it is in a persuasive essay.
There are essentially two ways to organize a personal essay: chronologically or thematically. You can start by choosing a theme and choose three points to develop for it. When you organize an essay chronologically, you are basically putting things in time order.