I've just installed nvidiabl module from https://github.com/downloads/guillaumezin/nvidiabl/nvidiabl-dkms_0.74_all.deb and screen brightness still is not changing. I have NVIDIA G210M, Precise amd64, VAIO VPCCW19FX
1-Downloaded nvidiabl debian base distributed version >> https://github.com/downloads/guillaumezin/nvidiabl/nvidiabl-dkms_0.74_all.deb
2- Installed it dpkg -i nvidiabl-dkms_0.74_all.deb
3- Add module to /etc/modules
4- Download oBacklight Script >> http://dev.osource.se/files/oBacklight_0.3.8.tar.gz (version 039 have an sh error try avoid it till is repaired).
5- Untar it tar -xvf oBacklight_0.3.8.tar.gz
6- cd to the untared directory
7-Give the script execution permission chmod +x oBacklight( I also change the owner and group to root but thats because im a little paranoid. You can avoid this.)
8-Copy oBacklight script to the /etc/init.d directory
9-Add it to the start up update-rc oBacklight defaults
NOTE: Depending on your laptop model, you may have to change the script mode. See >> http://dev.osource.se/docs/obacklight/
Ok now you're ready. In case you dont want to reboot now, just 'modprobe nvidiabl' and '/etc/init.d/oBacklight start' and test yourself.