|Isla under soft but directional window light.|
Say portraiture and many folk immediately think of studio pictures. I know a lot of folk with decent little cameras who run off to a place like Sears every time they want an updated portrait of a grandchild. I say try and do it yourself.
Seat your subject near a large window. Illuminate the subject with the soft but directional light. Watch for catchlights in the eyes. These are important. Catchlights add life to any subject's portrait.
While paying attention to the light, remember to pay attention to the shadows as well. Shadows give form to your subject. Here is a link to an excellent post discussing six simple and very popular lighting approaches used in shooting traditional portraits.
Your subject should be quite relaxed in this environment, certainly more relaxed than when forced to sit in front of a camera at Sears. With any amount of luck, you should be able to capture a pleasant expression. Don't struggle for a big grin. Don't badger the subject to smile or say cheese. Simply chat and shoot. Or do what I did and capture the subject unaware, pleasantly occupied with something other than picture-taking.
Today's cameras can take lots of photos without costing a cent. So, shoot lots and shoot fast. Don't shoot single shots but shoot short bursts. Keep shooting until you have your shot. Pay attention to the images as you capture them. You will know immediately when you have succeeded.
The shot of my granddaughter Isla was shot while she watched Caillou. She loves the cartoon Caillou and paid very little attention the camera. Unfortunately, she moved as I shot the picture and I cropped off the top of her head. Oops! If I took a little more off the bottom, the picture might look as if I planned the awkward crop.
Of course, I could have kept shooting.