I also face this situation ,but I found one maybe can help you -teach them chinese ,simple words ,sentence ,one by one .They will enjoy it and you will open your mind aslo.

if u cant follow what they are talking about,make them speak on topics you want. ask about weather there or what time is it there. dont be too inquisitive about personal questions. ask them if you visit their place for pleasure which things you must see,which foods you must not miss. and yes,dont forget to greet them and ask how are you. hope it helps :)

You can always talk about current events that everyone should know of, such as the recent death of Whitney Houston, etc. Similarly, if they are in your country, your city, etc., then, perhaps, they are aware of local events as well. If nothing else, ask them where they are from and see if they will tell you about their country. If they have time, and if approached properly, I feel most people with try to converse with you, at least for a little bit. I hope this helps and best of luck! J.

What do you mean by that ? you couldn't understand when they said or you don't know what you should talk to them...by the way, just feel free to talk like weather etc. and practice yourself more by watch eng/american movies without English subtitle and also listen to international song. Hope this help. :D