I always wonder how I can improve in English
One thing which i find very useful is to simply start reading books written in the language you are learning.
Im not sure about your level but try to find ones which are not too hard for you...
Make it a habit to look up on words which you dont fully understand. It will probably be tough in the beginning, but then as time goes by, it will get a LOT easier!
Speak English at all time.