Building your personality is one of the most important things if you want to clear your job interview. It represents how confidence you are.
Communicating properly with interviewer is very important. Interviewer should understand whatever you are explaining to him/her.
Before appearing in Interview you should constantly practice and try to improvise your as much as possible. As a wise man said "Practice makes the man Perfect!!"
Having knowledge is good but using it the way that it dosen't backfires at you is an art. Answering questions in such a way that Interviewer gets satisfied in the first response is very difficult. We prepare you for answering smartly!!