One word to mean “the proper way of doing things”

Solution 1:

canonical
• accepted as being accurate and authoritative: the canonical method of comparative linguistics.
• according to recognized rules or scientific laws: canonical nucleotide sequences.

Other alternatives include: established, orthodox, standard, customary, prevailing.

Solution 2:

To begin with, it seems to me that simply saying "proper" would fit your example nicely, although I suppose a case could be made that it's not the most tactful choice.

Beyond that, if you're talking about something that is formally anointed as proper: official, canonical, recognized, orthodox.

If informally considered proper: traditional, customary, normal.

Solution 3:

You might get some mileage out of the warm fuzzies of optimal.

Solution 4:

By the book. It may not be one word, but it's still fewer syllables than canonical.