1. Create New layer with parameters like belowe:
2. Fill this layer with black color:
3. Create new layer:
4. Now take Brushe tool and draw one white flexible line. With this line we will make experiments:
5. Now we will need to add some layer styles for this layer. So, go to layer styles. At first go to Outer glow and select parameters like this:
Now go to Inner glow and select parameters like this:
6. You see, we create fire line. Now all that you will draw in this layer will transform in to fire. So, all we need to do, is draw crocodile. For that open crocodile image:
7. From this image we need to make crocodile brushe. For that, we will go to Edit -> Define Brush Preset and named it crocodile:
8. Now we have crocodile brush. Open your fire layer and draw your crocodile:
We get very nice effect. Our fire crocodile is almost ready.
9. Now Duplicate layer with crocodile:
10. Pretty nice crocodile. Now we need to delete layers effects from duplicated layer. To do that, click on layer effects and pull them to trash:
11. For your duplicated layer add blending mode to Overlay:
12. Now take Smudge tool and draw some lines under crocodile and make crocodile teeths bigger. And thats all. We create nice fire crocodile. With this technique you can create many others fire objects. You can use all brushes that you have.
Final result:
More Tutorials: 
