1) Choose QuickTime 7 from the dock

2) Go to File and click on Open File... then select the video which you want to make a conversion

3) Go to File then click on Export...

4) Choose the encoding format from the list.

Tip: If you are looking for convenience, MPEG-4 is the preferred format.  If you are looking to encode in high quality, AVI is the preferred format.

5) Click on Save.  The file will be saved under desktop once its done