In orer to improve your english,you need to firstly figure out what are you strengths and weaknesses therefore you can imporve your english effectively.I guess most people would have problems with listening as teachers in school always focus on grammar.So in order to improve listening you need to listen to tapes,go to english corners and listen to english radio like capital FM.Furthermore improving speaking simply just require you to speak to people therefore your english accents would be much better.Finally writing i think writing is alot easier in comparison to listening as you are taught with sample sentences.so you can write a daily diary about your day in english or something.Overall in order to improve english just do things in english.get the second language into your life.(I hope that helped)