The following is a brief list of resources that may help you as you guide your child through this journey:
Youth Science Foundation: Smarter Science is part of Youth Science Canada's program for engaging youth in science and providing a curricular connection to project-based science and science fairs. This site provides many excellent links for all ages that can help your child plan, carry out and present a successful Science Fair project.
Science Fair Central from Discovery Education offers free resources ranging from getting started to presenting final projects. There is also a very good guide for parents.