Introduction:
I often read news which says one president or prime minister calls a president or prime minister of another country.
I assume the process is something like: someone (maybe a secretary) schedules the phone call. Once allowed the party wanting to call calls the other party. There might be a group of people accompanying the President or Prime Minister, with at least a translator (for bi-lingual situations) during the phone call.
I also assume even though there are lots of countries, which may or may not have specific protocols for government-to-government calls, at least part of the process could have some common protocols. Also, these protocols might be part of diplomat training programmes.
Now, the points above are just assumptions.
Question:
What are the general norms that are followed before and during such phone calls?
Note: If answers are specific to a particular country, it's fine. As mentioned earlier, I presume the process might not differ much from country to country.