In addition to the things
@Hydrocella listed, I also sometimes do the following:
- look for tennis Facebook and social media pages in the country and city I am visiting
- post on TW
- look for meetup.com tennis groups
- I have also visited local courts and just hit some serves or hit against the wall. Sometimes people at the courts see me and ask to hit with me. Other times I ask people I see at the courts.
- I have also visited local tennis shops to ask for people to hit with.
- Hire local teaching pro for hitting session or to play a match
A few of the countries I visit I now know some people to hit with and have even invited them over to visit me to play tennis.