Changing permalink of WordPress

You should never have to touch the mod_rewrite rules. WordPress flushes/rewrites them to .htaccess whenever you save settings on Dashboard -> Settings -> Permalinks. If that’s not happening, then something is wrong, either with your file permissions, or your local server setup.

Also, it is strongly advised NOT to use %postname% alone as your permalink structure. You will encounter performance issues the larger your site gets, with respect to number of Posts and Pages.