Start a new document 600x200 and fill the background with the color you will eventually want to have your fireball on. This technique will not look good if you decide to change the background color later.
Im using a dark black to blue gradient.
Press "D" to reset your colors to default black and white
Then create a new layer. No go to Filter->Render->Clouds
Now go to Filter->Pixelate->Mosaic and enter 20
Then Filter->Sharpen->Sharpen, do this 2 more times.
Now choose the eliptical marquee tool
and
while holding the shift button, click and drag to make
a circle towards the left at a size similar to below
Now go to Filter->Distort->Spherize. and enter 100 for amount.
Then Filter->Sharpen->Sharpen. Do this 2 more times
Now Select->Inverse then hit "delete". then CTRL+D to deselect.
Now Image->Adjustment->Color Balance (or CTRL+B).
For each Shadows, Midtones and Highlights, set its Color Levels as: [+72] [0] [-72]
Now select the smudge tool 
,
set the brush size to soft brush, size 35.
Now start and the right edge of the ball and smudge it
over to the right about midway. Do this from top to bottom,
all around the right edge.
Now duplicate this layer by draging the layer into the "new layer" icon at the bottom of the layer's pallete. (or just press CTRL+J). Then go to Filter->Blur->Motion Blur. Set distance=30.
Now select the smudge tool again, this time, set the brush to about 45. then smudge the top layer and create a long smudge from the ball to the right edge of the image.
Now set the brush size to 35 again, this time, smudge just above and below that longggg smudge, this one should be just a little shorter than the one in the middle
Now set the top layer's blending mode to "Lighten"
Now select the first layer (original ball layer), then go to Filter->Distort->Twirl. Set to about -75.
Here is mine:
More Tutorials: 
