Just found a super simply way to make a screencast whith osx (10.6.8):

• Open QuickTime;
• File -> New Screen Recording;
• Now click on the right side arrow of the window, and select your audio source (If you need to record some audio);
• Push the record button when you want to start recording;
• When finished, push stop recording button on the top bar, your awesome screencast will be saved on movies folder. If you want to select a particular format, you can click “Save as” and select which format you need.

No mess, it’s done.