GIMP Masterclass: An Excellent Trick to cut out images, even with fuzzy
hair!

A very easy way to remove a background from an image, especially if 
there is adequate contrast, including instances in which there is fuzzy
hair.

Video: https://www.youtube.com/watch?v=sg2f5y1M1Ac

1. Load an image, preferably one in which there is plenty of contrast
   between the image you want to keep and the background; for example,
   an image of a person with dark hair and clothing in front of a white
   background.
   
2. Use the lasso tool to roughly select the area you want to remove.
   This is important because highlights on the object or person you want
   to keep may have similar colors.
   
3. Then do "Layer --> Transparency --> Color to Alpha..." and select the
   most prominent color of the background.
   
4. Move the "Transparency threshold" slider and "Opacity threshold"
   sliders until you have your desired effect.
   
5. Repeat steps 3 and 4 as many times as needed for any other prominent
   colors in the background you want to remove while keeping the area
   you selected in step 2 selected.