If you are truly interested in the job, one thing you should do at the end of the interview is recap: (1) why you feel you are the best candidate for the job (give two or three of your strongest attributes and/or qualifications), and (2) restate your interest in the position by asking for the job. Do not expect the employer to make the first move. Let them know of your interest and desire to work for them.
If you want the job, tell me so.
It is interesting to note that fewer than 1 percent of all college students actually ask for the job. It's almost as if they assume their interest in the job to be a given. But it's not. So those who take this extra step will put themselves far beyond the rest of the competition. If I know that you want the job—that you really want the job—it makes my job as the interviewer that much easier and will greatly increase the odds of an offer either on the spot (it does happen) or in the very near future.
Remember that you cannot close the entire sale except with the person who can actually make the entire purchase. So if you are interviewing with Human Resources, close by asking to move forward to the next step in the process, which will likely require meeting with the Hiring Manager. When you interview with the Hiring Manager, you are ready to close on generating an offer.