Hello glenno
Welcome to Talking Point.
If there was a simple answer to your question we`d all be much happier and life would be so much easier.
It really will be a case of trial and error but I can make a couple of suggestions which you might try, things which worked for me.
1. Speak in very short sentences with just a single subject.
2. Ask questions which can be answered by yes or no or a nod or shake of the head.
3. Make sure your facial expression is pleasant, not worried or anxious or impatient.
4. Try not to offer choices.
5. Use visual clues.
6. Be tactile, hold or stroke hands, so much depends on the relationship you have.
Others might have more ideas. Ways which worked best for them.