Lets say you've tweaked your nvidia-settings configuration slightly to make things look better, possibly changed the contrast and saturation values in order to get more even looking colours and better definition. Maybe you've also noticed that these settings are not persistent between each boot, and require you to load nvidia-settings in order for them to have effect. This is quite irritating. A solution, however, is at hand.
It turns out that this is deliberate behavior on the part of the nvidia-settings program. In an instance where a computer has multiple users, you may want to have different configurations for each person. This is where your .nvidia-settings-rc comes in handy.
So open nvidia-settings and set it up the way you want it, once you've done that you want to navigate down to nvidia-settings configuration and click "save current configuration". This will then prompt you to save to your home folder, which is exactly what you want to do.
Nvidia settings can then be made to load the configuration upon login by adding
nvida-settings -lto Startup Applications under System > Preferences.
If this doesn't work, try running that command in a terminal. When I did this I was given output along the lines of the following:
ERROR: Unable to assign attribute RedContrast specified on line 40 of configuration file
'/home/sam/.nvidia-settings-rc' (no Display connection).
Luckily the solution is also fairly simple. You need to go back into nvidia-settings and untick "Include X Display Names in the Config File" on the nvidia-settings configuration tab, then resave the settings to your .nvidia-settings-rc.
Let me know if you have any issues!