Change default parameters I want to change the default parameter from '0.010' to '0.0001' of the select similar by area box. The parameter can be found here:
Edit > Face Select > Select Similar (Shift+G) > Area
The values are stored in the Startup-File if you change them after launching Blender you can set the values and save the default-scene as Startup File Ctrl-U.

You can also restore the Factory Settings from the Menu: File / Load Factory Settings.