Dear Raj,

Well, I think it is important to read as much as possible. This is an easy way to know new expressions. In addition you could also watch TV or go to the movies.
For your grammar doubts you should consider the website: UsingEnglish.com. There are many interesting grammar exercises. Try to do some of them and I am sure you will improve soon! I am an English student and this is one of my favorite English learning sites.
Don't you know any native speaker? Try to take every change to speak in English. On your next holidays you should possibly visit an English speaking country.
Have fun and good luck!
Maria