When sending out a conference bridge for international participants try to provide a local dial in number (e.g., freephone number for UK participants rather than a US toll free number)

Make sure to list the full phone number for accessing the conference bridge. For example +1 203 555 1234 rather than 555-1234 or 203-555-1234. Do not assume your international participants know local area codes or dialing patterns.

Provide multiple access numbers to call into a conference bridge. Some international mobile carriers will not allow calls to UK freephone numbers, for example, but if you provide a local dial in number for another country, your participants can still attempt to dial into the conference bridge.

Remember daylight savings time works opposite directions in the northern and southern hemispheres. Spring forward, fall back does not work in Australia. Also, thanks to the US Congress, daylight savings time changes at a different time in the US than the rest of the world.

I use that most often and include all the timezone difference in the agenda sheet.