A good Job interviews usually last about 40- 80minutes. Be conscious of this, however do not look at your watch. Always let the interviewer initiate the closure of the job interview. Try to detect signs that the interview may be coming to an end so you can finish your interview on a strong note.
When you come out of the interview room, you should review how you performed. A good idea is to jot these ideas down.
Ask yourself the following questions.

1)    How could you have done better?
2)    What do you think you handled well?
3)    What didn’t you do well?
4)    Were there any surprises during the job interview process?

By noting these down you are actually using it as a building block towards further improving your interview skills. Learn from any mistakes you make and make a conscious effort to fix them in future.

If you want to know how well you performed during the interview, you may want to call the interviewer after the job interview. You can ask them about your strengths and weaknesses. They will be able to explain to you, why they did not think you were suitable. Use their comments in a constructive manner.
Once the interview is over, it is a good idea to write a thank you note. Thank you notes can influence the interviewer as well as maintaining a strong network of connections.