In our time on mainly DS9 we learned such great lessons from the Ferengi Rules like 'Greed is Eternal' or 'Once you have their money ... never give it back.', but we didn't learn all of the 285 (286 if you include Quark's rule). So I thought that I'd make a thread and we suggest what some of them might be.
Memory Beta actually has an exhaustive list of all the ones established, not just in canon, but in TrekLit.
Not all of them. The book basically had all of those "authorized" by Ira Stephen Behr and Robert Wolfe at the time (many of which were not brought up in the show). It actually had an addendum for "new" rules "being discovered by you hew-mons every day" (i.e., rules the latter episodes established, that weren't in the book already). Anyway, the books also established a lot of "new" ones. Again--Memory Beta has a list of them all. But...there are still gaps.
Sex is one of the most beautiful, wholesome and natural things ... that money can buy. (regards to Mister Steve Martin)
There's one I remember from I, Q--though the Ferengi gives the wrong number for it ("60" is, alas, taken). "If you can't take it with you...don't go."