There are a few things to always do in a job interview. It's usually basic everyday things that you should do. The most important thing that you are looking at is making a good first impression.
Dress appropriately, as in whatever company you're trying to interview for you need to dress the way you think is most appropriate for the company. Most times you need to dress in a button up shirt and nice dress pants, which is the common and most appropriate thing to wear in a interview. You never want to over dress by wearing to much jewelry, nor wear to much cologne or perfume. Men usually need to be well groomed because the interviewer likes to look at those things and note it down. Be respectful, always have eye contact with the person to show you are listening. Never chew gum during the interview, spit it out. You need to treat them how you would want to be treated. Focus, nod head every once in a while to show that you've got the interviewers attention. Offer a firm handshake and have a friendly expression during the interview. Once your interviewer introduces himself or herself, make sure to take note of it and address him or her by it. If you didn't get it always ask for it again, because it shows a sign of respect when you use their name.
You always want to have good posture. Stay still, and don't be fidgety it usually shows that you have a short attention span. When you relax you can make the nerves of being interviewed calm down. Don't be too stiff because it can look sloppy and look very negative.
The tone you speak in during the interview could look really bad or really good. Speak in a positive tone, with a little bit of excitement and compassion of showing that you are happy to be there. Don't speak in monotone, because it makes them think you really don't care about what is going on. Be honest and be yourself. Nobody likes someone who pretends to be somebody else. Dishonesty gets uncovered sooner or later so be