1. Find or open a nice photo of flower or whatever you like. (I used Orange Rosebud)
2. Optimize it, play with levels. (My tutorial: Optimizing Photo).
3. Select Brush Tool and choose Soft Brush, 9px. You can find it under Basic Brushes palette.
4. Open Brush Pallete or just press F5.
5. Use settings similar to these:
Brush Tip Shape:
Shape Dynamics:
Scattering:
6. You can save your brush for further artworks by pressing this button:
7. Make a new layer and paint with white using new brush! For example:
8. Use smaller brush by pressing [ on your keyboard ([ - smaller, ] - bigger brush). Paint something like this. Use your imagination! :)
9. Set layer's mode to Overlay. Apply Outer Glow.
10. Reduce layer's Opacity to 80%.
11. Choose Eraser Tool. This time choose standard Soft Brush. Set Eraser's Opacity to 40%.
12. Start erasing some parts of our sparks.
13. Select your base layer, then go to Filter -> Render -> Lightning Effects. Play with light:
14. Layer -> New Adjustments Layer -> Photo Filter. I chose this:
15. Make a new layer above your base layer.
16. Select basic Soft Brush and paint some dots like these:
17. apply Gaussian Blur (Filter -> Blur -> Gaussian Blur) on them:
18. Set dot's layer Opacity to about 80%.
19. Hm, done ;)
More Tutorials: 
