My DS2's next school have recommended he brings a camera and takes lots of photos, too.
I've just been looking at Sugarcandy's link and the ideas about introducing the vocabulary of secondary school sound really good, and having a list of books/equipment reqd for each day, so they can pack their own bag the night before.
I'm lucky in that my DS1 already goes to the school so I can show DS2 his homework planner / filofax thingy that has his timetable in and events and homework, plus an area for notes to the form tutor. It would be useful to find out what your DC's school uses as DS1 received his on his first day, so there was no time to familiarise him with it.
The school have recommended e-mailing as the quickest way to get hold of the Senco, Transition TA etc rather than phoning as they move around the school a lot during the day, but always have their laptops with them. Even if there was an incident that would affect him that day. That's something you'd need to discuss with your school, best route for communication as it isn't always phone up like I'd expected.
Some areas will do accompanied journeys for the first few days, charity volunteers and the like. Perhaps the secondary school Senco would know if they do in your area.
Again I'm lucky that DS2 will go with DS1, at least on the way to school. The journey home can be more chaotic as the DCs are hyped up at home time and will all crowd on to the bus at the same time, not nice and calmly like the morning when there are various pick ups. If you are thinking of transporting them yourselves, the trip home from school may be the best one to do.
This is such a useful thread. I'm going to be checking it a lot in the next few months. Shall we put SATs worries on it, too, in May?