Although you can't expect to be perfect in an employment interview, you can do your best by
a. speaking forcefully but using some slang such as like and ya know to sound relaxed and friendly.
b. elaborating on your answers and criticizing the person or object causing the problems at a previous job.
c. occasionally refocusing and clarifying vague questions by asking Do you mean...?
d. showing some passion by bringing up a controversial topic and taking a clear stand.