Maintain a small book and note down 2 new words everyday to begin with later you could increase the number of words. just writing down the words is not enough try to make use of those new words in your day to day conversation. This way it strengthens your vocab. alternatively you could subscribe for word a day or any such stuff.
Always speak in English just don't mind if the sentence doesn't have proper grammar.
Read daily news papers, magazines and books. And while reading if u encounter new words make a note of it and understand its meaning and try using it in ur sentences.
All these were the advises given by my dad to do during my schooling... though i hardly observed ...