At this stage, this page is just here for discussion. Please feel free to use the talk page for discussion, and this page for substantive improvements. If we can get some consensus, perhaps we could later promote this to be a POLICY page.
Historically, Wiktionary operated for a long time without formal, written policies. During this time, various practices became broadly accepted among active contributors as "common practices". Common practices were not codified into formal policies, though they were often promoted through help pages, templates, and so on.
This system often worked, but it had the problem that there was no clear way for new editors to determine what was common practice and what was not; and there was no guarantee that even older editors would all agree.
More recently, it has been attempted to address these problems by formalizing common practices into policies (or into draft policies that later became policies), and recently Wiktionary:Votes was established to help structure the process and ensure that there was indeed consensus supporting these policies.
Nonetheless, Wiktionary still relies heavily on such uncodified common practices. Editors may of course cite uncodified common practices that are supported by consensus, but they are strongly encouraged to provide evidence that this is indeed common practice (e.g., links to relevant archived discussions). Even when they do so, it should be understood that a once-accepted practice might no longer have the support of the active contributor base, and editors are encouraged to challenge supposed "common practices" that they do not believe to retain such support. If it is indeed found that consensus is lacking, an effort should be made to crystallize the "common practice" as a draft policy, and, after discussion, to put it to a vote.
It is only by having these "common practices" properly documented, and voted on if necessary, that new and less familiar users can hope to understand what is in fact "common practice".