Here’s a story starter based on an e-mail or letter exchange. If you don’t have a writing partner, you can skip step three.
1. Create a character. Give this character a name. Jot down some key attributes: age, career, where the character lives, his/her relationship status, something the character likes, something he/she dislikes, something unique about the character’s past, etc.
2. Create a second character as you did in #1. Write this character’s information on a separate sheet of paper.
3. Give the information about your second character to your writing partner. In return, your partner should give you his/her second character.
4. Write a piece that consists of e-mails (or, if you prefer, letters) between the two character: the character you created in step #1 and the character you received from your partner.
For a model on how this can work in a novel-length work, check out Where’d You Go Bernadette by Maria Semple.