Step 1) Go and live in the country for at least 3 months. 2 years is better.
Step 2) Find light funny books to read in the language you are trying to learn.
When I went to live in Japan a young woman (a young woman no longer, alas) there recommended (in English) that I read (in Japanese) Patariro! She was right. It got me straight away. It's a manga, supposedly for children, but I noticed many adults reading Patariro! comics on the trains. The fact that it is "for children" made it easier for foreigners. The text was written in adult Japanese, with the pronounciation above it or to the side of the complex kanji characters. So children (and as a side effect foreigners studying Japanese) would understand it too:
When I came to Italy I thought I'd do the same thing. I needed to find a comic that the natives like. Unfortunately I found "Diabolik!" And it is. The plots are plodding and samey, the drawings are stolid and static. Look at this car racing along a road:
Now look at this Patariro getting a bit dischuffed:
Luckily my Italian studies were saved by Carlo Manzoni. A young woman (a young woman no longer, alas) recommended these two books:
"I'll break your nose baby!" and "I'll give you one black eye and another blue." hooked me in Italian just like Patariro had hooked me in Japanese. They are funny/surreal cop stories. I'd like to buy them again, but they're out of print.