For me, we always talk about the discovery in science. But if you are not really into something specific(like music, politics or even astronomy) or can't really express your view in the subject, just don't talk about it. Here are some common topics: TV series(common one like the game of throne), Movies, difficulties in daily life, sport(recommended), life experience, social network(stories about a friend of mine), games(if both of you play), poker game, food(seems easy but it is a hard one need to have enough vocabulary), family and lovers. Or just everything you are learning now.

Find something that you are passionate about. What do you like to do? If you like to watch movies, what about them makes it interesting to you? Think about the cultural differences between your country and a significantly different one (such as America). Do you eat differently? (chopsticks as opposed to forks and knives/spoons) How do people dress? Do you live with your family even as an adult as opposed to people in the west that tends to move out as soon as possible?

Cool , but I don't know as I can help you ... I am yet learning the english , but I'm always creating things news, phrases ... I'm brazilian and my name's Lucas . Nice to meet you . I gonna enter in the work now .. bye bye