Receiving a job offer after an interview is more than luck. It happens because you were ready! You did your research, you understood your skills and abilities, and you were able to 'sell' them. Even if your application and resume are perfect, it is the interview that gets you the job you really want. Understand that there are different types of interviews and each one needs a customized approach by you.
Check these sites for more interview preparation resources:
from Wayne State
from Virginia Tech
from San Jose State
Sample behavioral interview questions from QuintCareers.
from College Grad.
from The Riley Guide.
Mastering the phone interview from Monster.com