Exactly what Leigh said! This is how I learned Portuguese and how I am learning French now. I buy a nice grammar book with plenty of exercisies. I try to read easy articles, listen to music, watch videos and sometimes even try to watch easy to understand shows such as cartoons. It is also important to practice your speaking/pronunciation early on, so you can maybe read out oud, sing along with the radio or if you have someone that speak your target language, you can practice with them for a few minutes a day. Good luck. :)

A good English exercise book and a lot of hard work.  Also, by surrounding oneself with spoken English in the form of TV and radio.   Reading SIMPLE English books.