Ok... i saw some flame tuts already on here, but i find mine easiest to do. i will try my best to explain to you! Be sure to tell me how my very first tut is!!!
1.) Open up an image- it really works with any size, and i think thats why i like this method.
2.) Press 'D' on your keyboard-- that sets the colors to default black and white.
3.) Go to Filter-Render-Clouds.
4.) Next you need to go to Filter-Distort-Polar Coordinates, but switch it to 'Polar to Rectangular.'
5.) Then you go to Image-Adjustments-Hue Saturation. Click 'Colorize.' Then just play around with it until you get a fiery red-orage color... I usually use Hue: 18, Saturation: 100, and Lightness: +5.
And then you're done! I'm so sorry I didnt have screenshots or anything, but im not sure how to do it (as you can sorta tell, im a noob!, but if someone would please tell me how, i would be glad to put pics on here!
luv always
flo