At least for GNOME2, there is no need to manually place a script in ~/.config/autostart. Any file in the ~/.config/autostart directory automatically runs after you login to a GNOME session.
Create your script and add it to your Startup Programs under System > Preferences > Startup Programs.
I don't use GNOME3 so I can't say if this has changed.
Hope this helps.
Last edited by towheedm; 06-05-2012 at 10:17 PM.