Fire

 

Start with a new gray scale image (important), use a black canvas and put some clear heavy white text on it. Something like:

 

Select Image -> Rotate Canvas and select 90 CW to rotate the image 90 degrees clock wise. Then select Filter -> Stylize and Wind. If asked to render layer click ok, and then set the Wind filter settings as below. Repeat this at least twice, more if you want more flames. In this example I have done it three times.

Select Image -> Rotate Canvas and select 90 CCW, this should put the image back to normal. So you should have something kind of like:

 

Select Filter -> Blur and select Gaussian Blur. Just a light blur:

Follow this by selecting Filter -> Stylize and clicking Diffuse. Click of to this with the default settings on Normal. This should give you something like:

Now we want to give the flames a little bit of a ripple. So select Filter -> Distort and choose Ripple. You can adjust these settings to achieve different results, but some like this looks good:

Select Image -> Mode and select Index colour. Then select Image -> Mode and choose load colour table. Select colour table 'Black Body'.

Tada! A lovely fiery looking text. Adjust the settings to determine the height of the flames and how clear the text is to read.