This question seems to come up a lot so this step-by-step tutorial should make creating your own lens flares fairly simple. To create an anamorphic lens flare like the one found in the video below simply follow the steps below the video.
How to:
1: Create a new solid layer.
2: Apply a lens flare effect to the new solid from Effects and
Presets.
3: Place the "Flare Center" on top of the "Anchor Point" to line
up the various circles.
4: Apply a glow effect to the new solid from effects and presets.
5: Set the "Glow Dimensions" to Horizontal only (not horizontal
and vertical).
6: Increase the "Glow Threshold" to 100%.
7: Increase the "Glow Radius" to 1,000.
8: Increase the "Glow Intensity" to 5 or higher.
9: Apply a hue/saturation effect to the new solid from effects
and presets.
10: Under the hue/saturation effect click on the "small colorize
box".
11: Set your "Colorize Saturation" to 50.
12: Using "Colorize Hue" set the color of lens flare you want.
13: Finally, put he new solid in "Add Mode" so that it only
reveals the lens flare on top of your footage rather than the
entire solid.
14: Enjoy your J.J. Abrams-esque Videos.