Well here is a lightning effect that I used for this sig:
Well here we go:
1.Create a new document, size 500*200 and apply a standard Black and White gradient.
2. Go to Filter\Render\Difference Clouds
3. Press Ctrl+I to invert the image.
4. Press Ctrl+L and drag the middle arrow all the way to the right.
5. Now you can add it to any image you wish. For example:
6. Now we add it.
7. Change the blending-mode of the lightning layer to Screen.
8. Now we resize it and repeat the all the steps a few times and get this.
9. Now use a soft eraser with the opacity at 57% and flow at 38% and slowly erase the edges.
10. Now an extra step that I like to use is that I go to Filters\Colorefex pro and use the colorize option on the lightning layers and get this.
11. For a more realistic result, we'll grab the Brush and start brushing some blue on Mr. Vader and press CTRL+L on the lightning layers to make the bolts even sharper.
And that was my first tut in Photoshop, I'll do more if you like it and find it useful.