If you allow users to register to your WordPress site, then I would suggest you to look at the “Roles Manager Plugin”
WordPress Version 2.0 introduced the concept of Roles.
Each Role has a set of permissions or is allowed to perform a set of tasks called Capabilities.
If you allow anyone to register to your site, choose the “new user default role” from the general options menu to be “contributer”. This is the user with the least privileges.
Contributers can only create and edit their own posts.
They can’t publish their post or have any other privileges.
Roles Manager Plugin let’s you easily configure Roles and Capabilities of users of your site in a very easy to manage and granular way.
You can easily create new Roles and assign them any Capabilities you like.
The plugin has a great admin panel, you can access through the Users menu option.
To find more about it and download, click here.