The general answer is to find interesting materials or situations in which you will use English to communicate. Please don't think of improving your English as "studying" - think of it as your chance to express yourself to others. Do your best to understand what someone else is saying or writing.
Also, it helps to have a specific target. Do you want to be able to read an English language newspaper? Go to school in America or Britain? Get a good score on an English test? Whatever your purpose in learning English, it helps to have a goal to keep you focused.
Good Luck!