it depends.If they are chinese,well ,it is quite easy to get started to chat with them,using any topic.but you need to wait to see what can be interesting .well,if you are with foreigners,you just go ahead to ask where are from,such kind of thing. then continue.if you are talking about something really dull and boring,they would understand you.anyway,just show respect and your confidence.good luck,wish you can find some really nice foreign friends to chat with,and make big progress in english.