Find out where you stand and how you did on your interview before leaving your interview. Asking the following questions, in this order, will give you an idea. Be sure to ask these questions as they are stated, and in the order presented here.

1. "Do you have any concerns about my ability to do this job?"
The key here is to use the word "concerns," not problems or objections. Your objective is to identify their concerns and to try to manage them immediately, before they become a real problem. Their concerns may be unfounded, or simply untrue, and this gives you a chance to correct it. Also, DO NOT HELP THEM WITH THE ANSWER! Ask the question, and be silent. By helping them with answers, you may inadvertently create a problem where there wasn't one before.

2. "What skills do I bring to you that make me a match for your needs?"
This one is tricky to say, so be sure to make it your own. Your objective, after discussing the negatives, is to turn the conversation back onto the positives. Feel free to help them with the answers and encourage them to verbalize them as much as possible.

3. "Mr./Ms. [Hiring Manager], I am excited about what I have learned here today, and am looking forward to hearing some great news soon."
Asking for the job can make all the difference in the world, and it's the best way possible to wrap up the interview. The above is merely a suggestion, but it also demonstrates a polite way to ask for the offer.