Assuming you have a monitor that supports some high resolution, say 1680 x 1050, and you’re using an nvidia card:
- System > Administration > Hardware Drivers
- Make sure the latest recommended nvidia proprietary driver is activated (if not, do it and reboot)
- System > Preferences > Display (it should ask if you want to use the proprietary config screen – select ‘Yes’)
- Select X Server Configuration
- Set the resolution to what you want and ‘Apply’, then quit the nvidia-settings screen.
- System > Preferences > Display (when it asks this time, select ‘No’)
- Click ‘Apply’
- Click ‘Keep configuration’ (assuming everything looks OK)
- Click Close
When you reboot, everything should be preserved. I still notice a flicker on the boot-up screen when I think it tries to reset it to something else, but it should stay at the resolution you specified.