Some ways you might be sabotaging yourself:
--Negativity. I you think and "see" only the worst outcome, the interviewer may pick up on that. Also--don't be negative about former companies or bosses.
--Embellishment. Lying or exaggerating can catch up with you fast. Today's employers check a lot of sources, Recently in a CareerBuilder survey, 69% of employers said catching a lie was an instant dealbreaker.
--Bad body language. Don't fail to make eye contact, smile, and also don't play with something on the table or desk.
--Phone. Never check it during an interview.
--Homework. Employers can tell if you're interested enough in the company and job to check it out first.
Interest is good. I remember back when I was hiring people (when dinos roamed). If the person did not seem to want the job--didn't express this--I thought, "What the hey, I don't want that person."