according to my experience, playing RPG will enrich your vocabs,
as well as helping you out with exspressions, what would people say on certain condition.
the other way is, based on my experience also, watch the Simpsons several seasons in a rally.
why the simpsons? because it contains various kind of conversation, from the formal ones,
to the 'slang-ish' ones.
but if you want to improve your speaking skill, i'm agree with XPEN,
you should join a conversation club. Some of our state university have
the English Laboratory/club. some of our high school also have English club.
last one...
you can always try to contact one of our senior members of BF to ask them for help