This is a mixed bag at the moment. There are the manditory calls (I think inbound, joining and base calls) and apart from that its common sense. ie if some one is holding ready to line up, make a finals call just as an extra heads up(so to speak). But remember there is no requirement for a radio at all for CTAF aerodromes (unlike CTAF(r)), so really your eyes should be out of the cockpit at all times and broadcasts to a minimum req, with safety in mind for any 'extra' calls. That's what ive been taught anyway.
On the issue of climb out to 300' of cct height, I too was told that this is to ensure all aircraft are at cct height for the turn downwind without making the cct too 'wide'. Not really an issue for us 'lighter' aircraft as we are usually at cct height before you can blink. No problem turning xwind at 500 agl and still keeping a tight cct. Although as an xtra point we are required to follow those 152's forever till they can turn xwind. (such an annoyance... na just ribbin' ya
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