(This posting includes a handout which you are welcome to use with your students.) *
There has been a consensus among the many professionals that I have asked that dropping the final consonants on words causes the most communication breakdowns. I’ve had to decipher things like:
“I cou-n do my homewo cu I fe si.” (I couldn’T do my homeworK because I felT sicK.)
“Do you wan ah to chew a new topi?” (Do you wanT uS to chooSE a new topiC?)
If we just respond by asking, “What did you say?”, the speaker will merely repeat what s/he had said, perhaps a bit louder.
I developed a set of exercises that have proven to be effective in developing students’ self-awareness in the cause of some of their communication breakdowns. So now, if we ask “What did you say?”, the speaker will have a sense of the cause of the breakdown and of a way to adjust what they had said.
I asked him how he felt about it. He said that he was feeling discouraged because he really tries to be active in conversation, not only telling his ideas and opinions but also responding to and including other. So he 
Common Sense Teaching ESL 