How do I get started using Gettext?
For C/C++ developers here is a short and simple tutorial, that has everything you need to get started, in fact it's almost everything you'll ever need to know about Gettext. By all means send me an email if there is still something you don't understand.
If your code is PHP then perhaps this or this tutorial will be easier to follow.
Python programmers will probably find this or this website great for getting started with internationalization (thanks to Steve Ferg for pointing them out).