You have to find out what suits you best - for example: what did you do to learn English? What worked for you the best?
For me these are flashcards - I write whole sentences on them. I choose sentences half randomly (from texts, podcasts I listen to), half not (I'm using Serbo-Croatian frequency list to learn the most frequent words, it's on the web). Everytime I read my flashcards aloud.
Also: listening to podcasts, watching Croatian public tv, there are some useful things on youtube as well.
But the best thing for my Croatian was actually speaking - now I have friends I can talk with and it really really helped me a lot to write and to speak with them. At first it was half-English half-Croatian but now - despite being still around A2 level - I can speak quite fluently. But, of course, I have a bit easier situation since I speak another Slavic language:)
Good luck!