ATPM 14.04 - FileMaking: Getting Relational turns out to be a fairly comprehensive and quite readable introduction to relational database design. I didn't see anything that's FileMaker specific, it applies equally well to MySQL, Microsoft Access, Oracle, etc. (The promised f/u articles will be FileMaker specific.)
It's a handy reference to keep around for colleagues, students, etc.
Charles Ross covers a range of topics typically taught over the course of several lectures, so don't be surprised if it takes a while to get through the entire article. If you need to understand the topic, this is worth printing out and studying.