Would underline above comments and the thread highlighted by Fly Stim by repeating a comment I heard from a senior GA publishing individual last year:
"Untrained formation flying might quite possibly be the fastest way to kill two pilots".
I would venture to suggest that formation novices who attend our courses are surprised at just how many ways it is possible to mess up, and how detailed the formation Standard Operating Procedures are in order to make it a safe exercise. Our SOPs are lifted straight from the RAF - unsurprisingly, as they work well there and our instructors are already familiar with them - and students have to memorise these before starting the course.
There are a couple of good places where you can learn formation safely and professionally. Very happy to offer free advice and coffee at Kemble or Goodwood to anybody who'd like to chat about formation flying. Or any other form of flying come to that!