So, for whatever reason you want to get that special people portrait photo, I hope the following will be helpful to you.
Unless you are interested in what the person is wearing, you don’t really require the full body in the picture. A lot of photographers make this mistake. And that is accentuated when you hold the camera in landscape or horizontal fashion.
For example, there is your portrait - a standing, full body picture, in the centre of the frame, camera held horizontally and a whole heap of unwanted stuff on either side of the subject and unless you knew who the person was, their face is so small it is almost unrecognisable.
So, Select “Portrait Mode” on your mode dial or use aperture priority and put it on a large setting of say, F2.8 (to blur the background).
Turn your camera on its side, get in close, and fill the frame with your subject. After all, you only need what you want to see in the shot.
Be sure to focus on the eyes and if the subject is a child, get down on one knee to be at eye level or even lower for that matter. Try to as many varied points of view and settings as you can till you are satisfied you are getting the right kind of shots. If the child is busy doing something interesting include that in the shot as well. It could provide fond memories later in life.
The ideal lens focal length for portraits is around 130mm, wide angle lenses will only distort facial features at close range. So if your camera has a zoom lens, try to operate it in the 110 - 130mm range.
Select a neutral outdoors background, like a plain wall or green bush, with the sun behind you and to one side. Your subject should then be placed about 2 metres out from the selected background.
Other than the standard straight on look, ask your subject to stand at a slight angle away from the camera, but with the head turned in facing you, slightly tilted up or down. Use a bit of imagination with your posing. Anything is better than the plain straight-on look.
You could also choose the shade of a building overhang where there is a darkened background, with your subject facing out into the light. Providing the light is not harsh enough to cause squinting.
Slightly overcast days are also good for portraits and sometimes preferred, as there is less likelihood of getting heavy facial shadows. But a bit of fill-in flash from the camera or a reflector may also fix this problem, if and when it occurs.
If your subject is standing in the shade of a tree, it is better if it is all shade and not semi-shade or dappled light, as this causes a distractive mottled look, which can result in exposure problems.