IMHO, the 1st and 2nd rules are mutually exclusive - I see no need for any warning if there is enough room to pass safely. (Exception would be if there are other riders in front of the rider I'm going to overtake, which he might contemplate to overtake himself.) I reckon every signal, be it a bell or verbal one, is an annoyance - a minor one, and often necessary, but still - so I try to avoid it.