I agree with Baystateblue above. :-) Show genuine interest in your language partners, ask questions ( and pay attention to the answers!) and share your own experiences too. Try to begin new topics of conversation - don't just wait for them to initiate interesting conversation. :-) Add if they don't become good friends, don't worry, there are others out there who will ! I hope you make lots of new friendships.

I think you should talk about things other than just the languages in order to become friends. Maybe spend some time to catch up on how they are doing, discuss the news, and things like that.