- Make sure all images have exactly the same size
- Crop all images so that the size of the head is more or less the same
- Line up the eyes 1/3 from the top of each image
- Go for a close up, losing some of the top of the face if required
- Make the images black and white
- Increase the brightness of selected images if require
From the archives: a 2008 post on the same subject.