For instance, I bought all of my Pateks at ADs in Italy (including the limited editions), and at the time of purchase I normally just receive very standard gifts (at most a tie or a watchcase, etc.) Sometimes I don't even receive anything extra at all, but I get a good discount, which I prefer.
On the other hand, by dropping by casually for a coffee, over time I ended up getting all kinds of nice gifts (from hats to bracelets to scarves, plus all sorts of books; the very last one was a 2-volume museum catalog that's also on sale on the Patek site for $600+). The point is that I've been a regular customer of my main AD for 13 years, so over time I've become very good friends with him and also the daughter, and the nice gestures are therefore not necessarily related to a purchase.
So I don't really think there are many rules, except that human relationship is of course always paramount --- like in any other business, for that matter. And remember that the best attention you can receive will be the invites to private/VIP events and/or to visit Geneva --- in my opinion much nicer and more exclusive than the accessories!

Best wishes, and enjoy this fantastic hobby!