If you are taking a photograph of someone specifically with the aim of using it for artistic purposes, it is important to consider a few things.

Light and shade are important and with this in mind, it is better to take the photograph in daylight, preferably with the light coming in from one side. If it is taken inside, stand or sit the person next to a window so as to take advantage of the light coming through. If it is taken at night, place a soft light slightly behind and to the side, so that soft shadows are created. Do not use a flash!!

As for pose, the best portraits seem to be those where the person is looking slightly to the left or right. Try to get the subject to smile gently, but without showing teeth.