Another, slightly unconventional way (which is how I learned English as a native Croatian speaker), is to find an online community about something you really enjoy.
For me it was the combination of Harry Potter and online roleplaying[1]. I know that English isn't quite the same as other languages as it's quite widespread, but I believe it's possible to do the same for other languages.
I also improved my Spanish a little through a website called lang-8.com, but I am not sure how active its community is these days; when I joined it was new and the community was relatively small. I stopped using it since I lacked the time and motivation to pursue Spanish more vigorously.
[1]: As a side-note, I met my best friend this way; I was 13, she was 11 when we met. She'd would always go out of her way to help me with my English and would help me prepare for a roleplay and also analyse it afterwards, pointing out all the mistakes and potential improvements, taught me colloquialisms, etc. Although, everyone would help from time to time, too. So, meeting the right people/community also matters.
This is how I learned english. I fell in love with computers at an early age and everything from programs to documentation and the few communities were all in english. So I had to learn. I winged it at the time, just used a dictionary, some books, and whatever other resource that I found or fell on my lap.
I used to tell everyone who cared to listen that learning english would open up your world like you can't imagine (as it did for me). How many people even tried? 0. The common denominator is having to learn, and the only two ways that I've seen really work, is moving to another country OR having a strong interest about something and using a language to learn more about it (and you'll learn two things at once!).
For me it was the combination of Harry Potter and online roleplaying[1]. I know that English isn't quite the same as other languages as it's quite widespread, but I believe it's possible to do the same for other languages.
I also improved my Spanish a little through a website called lang-8.com, but I am not sure how active its community is these days; when I joined it was new and the community was relatively small. I stopped using it since I lacked the time and motivation to pursue Spanish more vigorously.
[1]: As a side-note, I met my best friend this way; I was 13, she was 11 when we met. She'd would always go out of her way to help me with my English and would help me prepare for a roleplay and also analyse it afterwards, pointing out all the mistakes and potential improvements, taught me colloquialisms, etc. Although, everyone would help from time to time, too. So, meeting the right people/community also matters.