I am no expert. Saw from Clubsnap about taking portrait photo.
Seems interesting. Its about depth of field.
1. Aperture, shallow depth of field, large aperture opening/ small aperture value.
2. Focal Length, zooming in.
3. Distance from Subject, closer to subject, shallower depth of field.
Well, I like to take portrait photos of kids, friends etc. Another thing to note, know what you want, say background and to how to make your subject looks best in photo =)