A keyboard shortcut a week
Since I remember I have, like most, been using keyboard shortcuts to save time on the computer.
The best bit of advise I can pass on is to learn as many shortcuts as you can.
I find that if you try and learn everything at once that the flood gates will never close and you will end up not being able to retain most of what you have learned.
So how do we go about it, try finding a task you do the most in a day and learn it's shortcut, for instance if you are constantly sending emails then you will need to know cmd+n, once you are in mail.app.
Now don't try any more until you think you will retain it, it may seem simple but once you start learning more it will be hard to remember them all, that's why I would say one a week is a good amount.
Before you know it your speed on the computer will be much greater and you will wonder why you didn't do this before.