I have been running science fairs successfully with my students for 12 years now. For new teachers, managing a project of this size and scope can seem daunting. Why not just copy what I've got so far and make changes where you'd like to make them?
This link will take you to my 6th and 7th grade Project Timeline, which has worksheets, guidelines and rubrics attached for most of the items that are to be submitted. Let me know which work best for you...if you'd like me to post something in particular, drop me a comment!