Are the communications between captain and flight attendants standardized?
Again, since there has been a sparsity of answers, I'll try to add to Simon's excellent answer and give a bit of a different perspective. My answer is dated in that it comes from flying 747-100 and -200 aircraft in the 1990s at the last airline I worked for. Given what I am sure is a wide variability of cockpit crew &amp; cabin crew communication practices around the world, it may still be relevant. Remember, though, this is pre 9/11.

The cabin crew typically would arrive at the airplane before the cockpit crew. The first interaction other than a quick hello as we came onto the airplane was usually the upper deck flight attendant coming into the cockpit within a few minutes of the cockpit crew (captain, first officer, flight engineer) getting settled. Company policy was that the upper deck flight attendant was to check with the cockpit at least every 20 minutes to see if they wanted anything. It's the captain's airplane, though, and she/he could set the tone. I always declined anything until we had reached cruise. Additionally, I would tell the flight attendant that checking every 45 minutes to an hour would be sufficient but that if they just wanted to come up to chat at any time that would be fine. We were usually flying 8 to 12 hour legs. I would also tell them that I preferred to be called Terry rather than Captain, though more often than not they still called me captain.

Company policy was that the purser (chief flight attendant if you like) was to personally come to the cockpit to inform the captain that "all doors are closed, all passengers seated." That was my cue to call for the before-start checklist. Likely the purser had already been to the cockpit earlier to let me know how the loading was going, who was in back, and any problems. I in turn would give the purser the expected flight conditions, estimated time en route and such. I wasn't big on the captain making announcements to the cabin. My policy was to give the info to the purser and let them handle cabin announcements as much as possible.

The next company-required communication was hitting the button that sounds the beep throughout the cabin when we climbed through 10,000 feet, and I'd turn off the seat belt sign then as well. If there were no weather/turbulence problems en route, the next usual communication was a call to the purser shortly before the start of descent. However, typically the purser would have come to the cockpit every couple of hours during the flight to chat.

Descending through 10,000 feet I'd hit the cabin tone button twice and turn the seat belt sign on.

Last cabin communication was hitting the cabin tone button and turning off the seat belt sign after the parking brake was set.

Hajj flights were a special case. The purser was always one of our people, but the flight attendants were supplied by the national airline we were doing the flights for under contract. The requirements included that the captain be notified if anyone became seriously ill. All Hajj flights were required to have at least one doctor onboard, who would be a Hajji as well. The purser would come into the cockpit to tell the captain, and the captain would ask if the doctor wanted to land for a medical emergency (they never did). The captain was also to be notified if someone died. This was not unusual on Hajj flights, and we carried body bags for that contingency. A death was not a cause for landing short of the destination.

There is an area that starts before descent that has religious significance to Muslims because of the proximity to Mecca. It was marked on the IFR en route maps. We were supposed to announce entering that area. I always did that personally because I had learned how to properly pronounce it's name (well, as close as I could). The irony of the situation was that here was a 747 from a Jewish-owned airline, captained by an atheist, telling a plane load of Muslims they were approaching Mecca, Islam's holiest city.