Allow users to edit only their own posts?

I have a blog-type site where users login and then post their own stories. How do I give them the ability to go back and edit their own posts after they’re posted? I’ve found a couple plugins that claim to allow that function. But when I tested them under a user account (instead of admin), it seemed to allow me to edit everyone’s posts. I just want users to be able to edit their own. I found a couple other plugins that seemed like they might work, but they require that I go in and assign every user a role individually. Is there some kind of plugin out there that just automatically allows users (contributors) the option to edit their posts once they register with my site?