To start with open your picture... for this I chose a day scene (but any will do)

NOTE: if there are people in the scene they must be isolated and colored separately.



Now go to [Image > Adjustments > Gradient Map...]



Make yourself a new gradient that looks something like this...



NOTE: Keep in mind that you might have to play with this the most... till you get the look you want.

Now it should look like this:



Next through in a "mild" Gaussian Bur... [Filter > Bur > Gaussian Bur...]



Then add some noise... [Filter > Noise > Add Noise...]

And you will get something like this...



Well that's it for now... not the hardst thing but it is my first tutorial so I thought I would keep it simple...

-Eamon

Thanks for posting this. The disadvantage to this effect is that the colors are based on the original brightness values, whereas real infrared images show heat. So technically these images aren't really...correct, per se, but they sure look good! :D Thanks again for posting this tut.