Show the child samples of good photography and have him/her try to emulate them as well as emulating you if you are also in the art. This shows them the different techniques, angles, perspectives and soon he/she starts developing his/her own style.
Make sure to allow him/her to photograph as many subjects as possible and take him/her to photogenic locations. giving him/her access to photo magazines/books also helps.
Note: it is also important to have the child become familiar with the camera settings and to understand the rules of photography such as the rule of thirds.
Allow him/her various lenses (as your budget allows) to awaken his/her creativity.