Stress your qualifications. Present your work record, references, or other material to support your statements when they are requested. Don't criticize others. If you are asked about a previous associate or employer, say something positive. Don't be afraid.
Most interviewers are patient and considerate.
You have something to offer. Keep your courage. If you don't get the job, accept the fact that the job was probably not suited for you or you for the company. If you made a good impression in the interview, the employer may refer you to another employer or put your name down for future reference if another job opportunity becomes available. It is up to you to be successful.