How to ensure that all new users have the same profile settings as the current user? I am using Ubuntu 12.04.
/etc/skel/. Anything you shove in there will be copied out to a new user profile when you create them.
The most meaningful way to use this in practice (for deep customisation) is to create a user, customise their account to how you want all the others to look and then copy things in that profile out to
One note: a lot of applications will create home directories on their first run. Because of that it's important you only run the things you want to customise under your template user account. Otherwise you'll end up contaminating things that don't need to be there.
Second note: You may need to update the template over time as default applications change. It's not a long process so as long as you spend 10 minutes testing a new profile each release upgrade, you should be fine.