Like any other language, you have to use it to learn it. Making a conversation in English is no different than making a conversation in Chinese. Unless you make the effort and take the initiative, nobody is going to bother coming to you. Communication is more than just learning the slangs and idioms. There are people who are poor communicaters in their mother tongue as well. No surprise they are having problems with the second language.
The topic has to be interesting to everyone. Start with something you feel comfortable with and control the conversation around that topic. I often find it is hard to struck a converstion with the younger age group. It seems like I have more in common with people 10+ years older than me. For either men or women, asking about their kids always get them talking. The new movies, vacation plans, investment, etc, all sorts of things you can talk about. I don't like the bar culture and am not interested any sports or pop stars, that is one reason I found it is hard to mix in the younger group. I will wait for them to grow older.
Participating in group acitivities helps build up the relationship and improve your conversation skills. I golf with a group people at work in the summer time. Golfing is a good sport, because you have to walk together most of the time, it is hard not to talk about something. I played volleyball with another group of people last winter. This is not as effective as golfing. I think I will move on to something else next winter. Maybe something that needs to take turns, people have to wait in line. That way we can chat as we wait.
I used to think taking courses would help me make local friends. It had been proved wrong. Unless you are very outgoing, nobody will come to talk to you. And the break between classes are only 10 or 15 minutes. I always end up making friends with the immigrants in the class, because they feel the same as me.
If you live in a house, your neighbours are always a source for friendship. Last year I wasn't around much, someone cleaned my driveway for me. I am planning to bring him a bottle of wine once I find out who he is.
Inviting people you like either from work or other venue of life to your house parties is another way to stengthen friendship. I have at least two house parties every summer. More cocktail/potluck style rather than having a feast. That way we get to talk. That said, I'm sure I will be invited to one or two house parties as well.