The mark, writing, paper and printing, and later the press.
Begin, on day one, the deliberate transfer of what you know to people who will outlive you.
Needs first: Decide how you decide (Society)
Move knowledge out of heads and onto something that outlives them.
Needs first: Start the record, Pottery and the first kiln (Materials)
Make a cheap, plentiful writing surface.
Needs first: Water power (Energy), Writing and the durable record, Alkalis (Materials)
Make copies faster than people can write them.
Needs first: Paper, Machine tools and precision (Tools), Steel and heat treatment (Materials)
Let anyone publish without a licence, protect what they publish from punishment for criticising the powerful, keep the media many and independent, protect journalists and their sources, and hold the press to correcting its own errors.
Needs first: Printing, Constraint on the ruler (Society), Published rule and the court (Society), Telegraph (Computing)
Every guide, build, reference sheet and book reached from the steps above.