Hi Bindu
In my view you should help them be motivated enough to attempt to communicate in English at all times. Perhaps giving them practical exercises like solving simple crosswords, identifying the main points and sub points from a group of related sentences, asking them to use the right synonyms to fill in the blanks etc. could prove motivational.
Focus on correcting their tendency to lapse into directly translating their thoughts from the vernacular to English.
Most people are too lazy to write and construct the sentences as a result they tend to simply verbalise their thoughts which you may correct but which may not be fully understood or grasped. Give them ample written work which can then be corrected.
You may also find the contents of the following blogs useful if adapted suitably to supplement the learning of the English language skills. E.g. You can give them the quote of the day and ask them to write on it. Then you can give them the thoughts articulated in the blog or you can give them a Word and ask them to use their imagination to generate an acronym this will stimulate their thinking and force them to think of new words.
www.actspot.wordpress.com - Daily Blog
www.poweract.blogspot.com - Weekly Blog
Best Wishes