I notice at interviews that sometimes a candidate doesn't really seem to know how to finish out their answer or when to stop talking! You can help yourself by knowing how you will end each of your competency answers, so that at interview you will feel comfortable with your finishing sentence and know when to stop.
Know how you will finish your answers for job interview questions. Finish the answer and stop talking. Be comfortable with any silence that happens at that point. If your interviewers want more detail from you, they will ask.
My interview tips are based on my years of interviewing experience and my years of interview coaching. I hold qualifications in HR and Business Psychology.