How to film on Canon EOS 500D

• set the Mode Dial to the Movie mode
• then the AF-On button to set the focus
• then press the Live View button on the rear of the camera to begin recording (with the same button ending the movie). 
• Although you can autofocus during movie recording, the camera uses the painfully slow contrast-AF mode, and even the user guide warns against trying to auto-focus. 
• Focusing manually is a much better idea, although most AF lenses have MF rings with very little 'travel' between their close-focus point and infinity