I guess the advice I received only really applied to highways, because 30 zones are typically the places where you barely want to go above 30 anyway.I dunno, I tend to go along with traffic when there's people around me but I go within 5 mph of the limit by myself just to be safe, but my driving teacher's said 9 is okay.
I think some other advice is that there's no such thing as overuse of your turn signal. At the same time, you don't want to use it too early to mislead the people behind you, though, depending on the situation (like if you're signaling to turn right, but you want to take the third right from the point in which you started signaling from, as opposed to keeping a right turn signal throughout the highway).