1. When people write a story, add a very prominent field with space for email addresses of friends and family who will be interested in reading the story. You may want to use the google API to get contact information from the persons friends, allowing an automatic sending to ticked friends
2. Add a photo or avatar of the user beside the story. On the fp, add a bunch of faces of recently logged in users. It will instantly feel more like a community, and if you encourage people to use their real photo, things will stay very civil
3. Make a weekly competition. Make it prominent on the frontpage, and make the payment amount very small. For example, $10 by paypal. This is just $40 a month. Encourage people to invite their friends to come and vote for them. The best story each week wins the $10 and so on.
4. Find your target audience. Post on forums that do the same stuff
5. Allow people to write serials. For example, for a long time I used to write the fictional account of a soldier at war. I did this over years. Each entry was a short story, but together they formed a long narrative. Such long running narratives build fans
6. Allow pictures in stories
7. Here we will become a bit unethical - search usenet for an obscure but funny story. Add it to your site. Link it from reddit and digg. Alternatively, search scribd or any other document site for the most popular documents of all time that are stories. Addd to your site and do stumbleupon on that
8. Add a 'whacky' category where strange stuff is added. This stuff is more likely to be linked to than the serious stuff you want, but will drive traffic to your main site
9. Don't let your users drop off. If I sign up once, I have to get regular notifications about something, so I get invested in the site
10. Everybody just wants to have fun. You're entertainment first, don't forget that.