Experiment with poses and angles. Try different twists the body, head, facial expressions, perhaps lighting options. It is important not just to make some many different photos, and make some excellent shots.
Pictures of children is not easy. They are and strive to turn away, yawn, or made a face, as if they were not interested in acting, the good pictures you do not get it. Try to interest the child. Let parents bring a few toys, and if you have your own studio, then lay up some entertainment for young children, interesting and fun props.
If you're shooting a close-up, then make sure that the person attended the photo entirely. You can crop the picture so that the crown, for example, will be cut, but it should be your decision and not an unfortunate accident. When are focused and know what you want to highlight in man, Focus on the eyes, so you will not regret it.
As for the technical aspects, the portrait lens - this is very important. Wide-angle and bright, it can make your portrait photos completely different, if you've removed the universal or fairly simple optics. Recommended conditions for portraits is open diaphragm, which provides the lowest depth of field.
Also ensure that there is in the background. All kinds of poles and lamps, so out of place "grow" out of my head after shooting is finished - not uncommon. Get used to estimate the background right, then to the extra elements do not spoil your shots.