Five sizes: a display size, a heading, a subheading, body text and a caption. Every application an identity has to survive can be set in those five, and every size beyond them is a decision somebody will make differently next year.
The request always sounds reasonable
It arrives around week eight. A brochure needs a size between the heading and the subheading, or a sign needs something bigger than display. We have learned to treat the request as a layout problem rather than a type problem. If the heading is too big for the brochure, the brochure is set on fewer columns, and the heading fits.
Tabular figures, always
The one thing we do insist on adding is tabular numerals. A bank, a transit authority and a publisher all print columns of numbers, and a proportional figure in a column of prices reads as a mistake even when it is not one. Every type family we license has to ship them, and the guidelines show a table set both ways so nobody has to take our word for it.
How the scale is written down
One page. Five rows. The size, the line height, the letter spacing and the weight, and a sample of each set on the grid. A designer who has never seen the brand can set a page from it in an afternoon, which is the whole point.