The system has some presets which are stored in /System/Library/User Template. Inside this folder you will find subfolders such as English.lproj, French.lproj etc. The idea is to create a user as you want it to be and replace the corresponding template with this user’s home folder contents. If the system language you use is English, then you’ll replace the English.lproj folder. If your system has another language, you should replace the corresponding language folder.
Firstly, create your user, let’s call it “sample”.
Log in as the sample user and set it up as you wish.
Log out and log in as yourself (you should have the permission to administrate the computer).
Then, I strongly recommend to keep a backup of the User Template folder before doing anything else. So, open the Terminal and type the command:
sudo cp -R /System/Library/User\ Template /System/Library/User\ Template1
You will be asked to give a password; type your password.
You should now see a folder “User Template1” right below the “User Template”.
To delete the system’s template, in the terminal window type:
sudo rm -R /System/Library/User\ Template/English.lproj
Then, copy the sample’s home folder:
sudo cp -R /Users/sample /System/Library/User\ Template/English.lproj
The change takes effect immediately.