I would probably be accused of making more calls than necessary by some of the experts here, but I make them so that others are aware of what I'm doing. One of my big bugbears is incorrect position reports particularly from converging traffic approaching airports I've seen them as far as 5 miles different to where they say they are this is very dangerous because if I hear a call from someone saying they are in one place which will be no conflict to me I'm no longer concerned with that aircraft. The calls and reasons I make them are below.
Entering
Traffic xxx, ABC enters and rolls runway 11 for a left turn, departing overhead, tracking to intercept 274, climbing to 6500, xxx.
This lets traffic in the vicinity of the airfield know exactly what my intentions are.
Departing (this call on both CTAF and Area)
CTAF - Traffic xxx, ABC departed overhead time 25, established outbound 274, climbing 6500 passing 3500 xxx
Area - All stations xxx, ABC departed overhead time 25, established outbound 274, climbing 6500 passing 3500, yyy at 40, if centre don't do it automatically (and they often do) request the current area QNH.
This lets traffic (CTAF) further out (but inbound) know what my intentions are (they may not have been on CTAF at the time of my entering call) and my current location as we maybe conflicting through various levels.
Area call lets transiting and inbound aircraft (possibly not on CTAF at that time) know my intentions and current location.
Inbound
Area - All stations xxx, ABC is 30 GPS to the west inbound on descent left 9500 tracking for a 5 mile final RW 11, 5 mile position time 15
CTAF - Traffic xxx, ABC is 30 GPS to the west inbound on descent left 9500 tracking for a 5 mile final RW 11, 5 mile position time 15, xxx
CTAF - Traffic xxx ABC is 10 miles to the west inbound for xxx, passing 4500, tracking for a 5 mile final RW 11, xxx
CTAF - Traffic xxx, ABC established 3 mile final RW 11
All pretty simple really, doesn't take up enormous air time and no one is under any illusions as to what my intentions are, the key is knowing what you are going to say before you key the mike.
Aldo