1. Get Greasemonkey (https://addons.mozilla.org/de/firefox/addon/748/) and install
2. Go to your last.fm profile page (http://www.lastfm.de/user/YOUR_USERNAME_HERE)
3. Right-click on the Greasemonkey Icon and select "Add new Script"
4. Enter a Name for the Script and make sure your last.fm profile is already insterted in the dialog
5. Copy the code from the userscript.js in this repository and paste it into your editor.
6. Go back to your last.fm profile and tweet your songs ;-)

If you encounter any problems feel free to send feedback to me.