The number one thing to understand about the science fair becomes the science itself plus the thinking used to make sense out of the results of the experiment. This sheet shows the kind of things a judge must assess and although the board has a place the sheet, it shows most of the points come from the science itself. Make sure your student can easily talk about their project.
NASA has tons of resources and even workshops for teachers to help students. This site does a good job on teaching the art of science observation. A video with transcript helps make sense of the information given. It segments each step of Science Fair and gives information for each piece.
Preparing for a science fair may mean doing a series of mini experiments to determine what concentration the final project should have. Preparation for science fair becomes easier when families do mini experiments all the time. It starts a discussion and makes the thinking process more fluid. When science fair comes, a student has practiced many of its parts and can concentrate on the induction and deduction aspects.
A video done in a fun way for doing a science fair project. The setting happens in a school and begins with the angst of it all. Then it goes through in a detailed manner what the scientific process is.
These books are developed by theme and have experiments listed with suggestions. It has the experiment materials listed with the process as well. It will not be enough for a full blown science fair, but by offering a framework it gives students more time to do deep thinking and creation rather than glossing over the science concepts.
List of experiments by grade level with videos. It could serve as a starter point for science fair projects, or could serve as a supplement to a science fair process or even to help understand a concept.
An online science competition for 13 to 18-year-olds globally. Takes only an Internet connection and a Google account. Details vary according to the country and it can be completed in teams, and the site also includes general science information.
I remember the hardest part about science fair as a teacher began with gathering enough information for students to develop a project. This site has lists of ideas and pictures. It acts as a good starting point for developing an idea. It would be a good family resource as well.