Useful starting points
Use professional titles where the setting calls for them, then follow the other person’s lead.
Allow time for relationship-building in client-facing contexts.
For public-sector, diplomatic or highly formal settings, verify protocol rather than assuming ordinary business customs apply.
Culture is context, not a script.
Individual preference, profession, generation, region, language, organisation and the specific relationship may matter as much as nationality. Observe, ask respectfully and follow the host organisation’s guidance for formal situations.