A cousin of mine who is in tenth grade or so wrote me this: "I love writing but the idea of just starting an essay with no thesis and taking it in any direction I want to intimidates me."
I'm sure she's not alone. People have all different writing styles---some make copious notes and know exactly what they want to say before they write and others just jump in without a plan. Most successful personal essays though seem to be involve someone sitting down and kind of doodling around until the piece coalesces, and in fact this is how it usually works for me. (Is this indeed how it works for everyone? I'd love to hear input from other writers.)
If you want to write an essay, but aren't sure where to start, it helps to begin with something that interests you or bugs you or confuses you: an image, something you saw happen on the street, something like "I used to be close friends with person X and we drifted apart---why is that? What changed?" You start explaining or investigating that on paper and see where it goes.
Here are some other ideas:
* Describing an early, vivid memory (maybe your earliest) is always a good one. I was assigned this in a great course on memoir with Patricia Hampl, who talked about memory as an ocean, where you look out over this glassy surface and then dip down and grab something from underneath the water. I looked back over my childhood and grabbed this memory of a tick-covered cat that we found while living in Clemson, South Carolina, and of trying to remove the ticks and having the cat run away. That was the whole memory. So I wrote that down, and then I started writing about childhood in South Carolina, and then I realized that the cat represented a loss of innocence---the first time I could remember feeling really broken hearted, because we couldn't help this animal, and that's what the essay ended up being about.
(By the way, the difference between essay and memoir, and if there is a difference at all, is another topic.)
* Describe a map you have owned or used. This is one I made up for some class I was teaching or taking, and I just like it.
* Pick a word, maybe at random out of a dictionary, and start writing about it.
* Pick something you are good at doing and explain it. Like playing a difficult guitar chord or talking to strangers. And then think about a specific time you did it and why you are good at it, and why other people aren't good at it, etc.
* Joni Tevis, whose lyric essay I posted about, says that when she writes she likes to put two very different objects together in a piece of writing. She metaphoricially holds them next to each other and says, do they go together? No? How about these? Try that yourself---maybe I can start writing about bicycles and cats--any overlap? How about my mother's cancer and my obsession with Star Trek? My inability to pass geography in 7th grade and my love of Russian dance? One great essay that does this is "I Bought a Bed" by Donald Antrim which is unfortunately only available online to New Yorker subscribers. Antrim writes about his mother's death and his quest to buy the perfect mattress. It works beautifully.
I'd recommend avoiding the stuff like "pick a time when you overcame an obstacle" that they make you do in school, because then there is a foregone conclusion built in that can hamper you and you end up with some Aesop Fable glush. It's nice to not know the answer when you begin.
Any other favorite prompts?