A few things that I believe may help in an interview. It depends on the type of job etc but it's always good to have a few questions for the interviewer. It shows a greater interest from you and is something an interviewer normally doesn't see...it's good to separate yourself from the crowd.
The other thing...get the interviewers name and address. When you get done, make sure to send them a handwritten thank you card (give them appreciation for their time...it also keeps you in their mind).
If you are asked about weaknesses...turn them to positives. My weakness is I like to be really organized and sometimes it's not needed...When I'm doing a job, I have to remember there are people who aren't as meticulous as I am or not as experienced or not as eager to learn and I have to make sure I don't become impatient but since I know about this, I take special care to help others have the same motivation I have. This is much better than saying I get pissed when people aren't working as hard as I do and I have trouble with my temper.
Eye contact, eye contact, eye contact...If you have a problem with looking people square in the eye...look at their eye brow or just below the eye...
Listen don't just hear. Everything the above have stated are good. I say downplay weaknesses and empasize your strengths...but that's just me.
Have a plan of where you want to be in 1 year 3 years and 5 years ( in their company)...Ask about upward mobility (even if there isn't any). It shows an eagerness to learn and wanting to expand. If you have a job history...make it one page. More than a page, interviewers get bored and quit reading. Bold type the position and years. They don't care about months and days. Show special interests, clubs, hobbies at the bottom (briefly). This gives them something to break the ice with during the interview. If you know the job...tailor the information for that job...don't leave gaps in years but emphasize information that would go to that particular job. Again, make everything brief but very informative. Make sure you don't have typos!!!!
There are a lot of books out that tell how to interview, do a resume' and get noticed. The information in them works. One thing I remember in one of those books was "remember, there's already a king and a president...don't ask for their position or their salary!" I was asked what type of salary I expected one time and I paraphrased that...it stuck in the interviewers mind well enough they offered me a job.