Why do you want to do this? Is it the irritation at typing "sudo" so
often? That bothers me too, so I use the "-s" option to sudo to get a
root shell. A bit dangerous, but no more than having a root account
that you can su to.

jbuchana@zaphod$ sudo -s
[sudo] password for jbuchana:
root@zaphod#

Much nicer than typing sudo until your fingers are nubs.

I might want to point out to any people without a lot of experience
that this is a bit dangerous, more so than having to think and type
"sudo" every time you need it, so be careful!

Because I'm paranoid about security. My computer has only one user - me
- who has full admin rights to the box. I personally see this as a
security risk - mainly as my computer is permanently on with me logged
in. I want to separate out the admin tasks and the day to day tasks so
that, should my computer be compromised, it becomes that little bit
harder for the hacker to do any serious harm. I want to limit my access
to those few tasks I perform regularly, while reserving the more
dangerous and less frequently used commands for root access only. Yes,
I know that I have to type in my password for sudo to work, but I don't
actually see that as a serious line of defence.

And also because I simply want to learn how to do it :-)

It's no real problem. Use SU. Log in. Close the Term Window when you're done.
Root then goes away...

Well, yes, I know I can do that - that's the point of this exercise, to
protect the dangerous functions behind a second, stronger password - but
it doesn't help with my second objective of learning how to write a
sudoers file. I don't just want to use this machine, I want to learn
how it works as well