Making Photos Look More Dramatic/Sexy
Here is a technique for exaggerating the light and shadows in your pictures.
Step 1: Open your image. For this tutorial, we'll be using this photo from Flickr by ruguay:
Step 2: Duplicate the image's layer 3 times so you end up with 4 identical layers:
Step 3: Select the first duplicated layer (I've called it "No red"). Then go to Colors > Components > Channel Mixer (It's Filters > Colours > Channel Mixer for GIMP 2.2). Make the settings in your channel mixer match the following and click OK:
Step 4: Now select your second duplicated layer ("No green") and repeat the Channel Mixer procedure again; except this time, set Red to 200, Green to -200 and Blue to 200.
Step 5: Select the final duplicated layer ("No blue") and again repeat the Channel Mixer procedure: Red: 200, Green: 200, Blue -200
Step 6: Set all the duplicated layers' modes to Overlay. You're done!
If your image looks too dramatic, you can experiment with different opacity levels for the duplicated layers. Enjoy.