If you're looking to improve your verbal fluency, I would absolutely recommend lots and lots of television. Find a show you love, watch it lots, and try to copy what the characters say -- in rhythm and intonation. Even better if you can find a show where there's a character you identify with, an actor who is similar to you in "type". Get closed-captioning transcripts of episodes and try to say each line before and then compare with how it's actually said. I would say this is absolutely #1.
I see other recommendations here for Toastmasters and for improv comedy. Toastmasters is specifically about public speaking -- if that's your goal then absolutely, but if you're looking to improve personal conversation I'm not sure it will help much. And while improv comedy is a blast (I've done lots myself), I don't think it's going to help much with linguistic fluency. There's a ton of focus on physicality and teamwork, but it will go much better if you're already very comfortable with your speaking.
All of the best students I ever had in English classes would basically watch the TV show "Friends" for like 2-3 hours a day, I'm not even joking. It's surprising how well the TV route works. And after that it's really about practice -- figure out whatever situations you can have a lot of conversation with native speakers in, if there's some kind of local club/activity you can join.