Thanks for starting this thread OP.
My niece would love a family unicorn 
My son starts secondary in September. There are about 12 from his school going including three of his besties plus children he knows from other clubs he does, so that's fortunate. He's winter born, outgoing, bright and NT so no concerns from those perspectives (luckily).
He has been ignoring the thought of leaving his [beloved] primary but they had a visit from the secondary's "transition leader" last week which seems to have been well enjoyed. DS will spend the day there in 2 weeks time. They also run a 3 day "transition camp" during the school holidays for the new year 7's to get to know each other and the school. Which I think is a good idea.
In terms of what prep. I've done - I have ordered some school uniform, opened him a student current account, paid for his locker, purchased the iPad and installed all the required apps. He got a phone for his birthday. The school is a little over a mile away but there is a bus he could take if the weather is bad. We'll spend more time on the journeys over the summer.
I'm a little apprehensive about it. Mainly because I'm a control freak and I know everything about, and everyone at, his primary and that's obviously going to change!
It will be great; the school has just had a wonderful first Ofsted report, the parent survey results on the Ofsted site are all really good and the extra curricular clubs are awesome (I'm considering self-identifying as a Year 7 so that I can go too
)