As someone who taught English as a foreign language for many years, I'd say it really depends on where your specific difficulties lie.
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.
We need to group-build a mapping of (language -> most appropriate mainstream TV show) because every english as a second-language person I've met and discussed learning English with has told me this about Friends. But what should I watch to further my learning of German|French|Latin|Ancient Greek|...?
I don't know whether it's a better suggestion, but telenovelas (and there are plenty of those) will likely help one learn Spanish better, or better Spanish, while using more realistic intonations and voices, than El Chavo del Ocho with its adult actors making child-like voices and using many expressions you won't find in real-life conversations.
I'm an amateur student of language acquisition. I can only add to this, because I think you're spot on. I knew a few people who landed here on their own and within a few years had no appreciable accent. ALL of them did this by living away from people who spoke their own language. Just too easy to slip into it when you've had a long day cleaning houses or working in an Amazon warehouse.
EDIT: Hilarious typos in a post about language acquisition
> 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".
The problem is I'm a smart-ass and people don't like me speaking like Archer.
But seriously, I got way more comfortable understanding spoken English by watching seasons of Supernatural. I would only add that I found subtitles very helpful because understanding an accent you're not used to is very hard without a little help. An alternative being watching something you already watched in your own language so you know what's going on and can fill the holes.
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.