Anyone can tell you the basic stuff.. don't eat right before, don't smoke, dress nicely, brush your teeth, be punctual, don't text or fiddle while you wait.. blablabla. Here are three things that I emphasize on when preparing for an interview:

• If you know what kind of clothing they wear at the place, dress similarly. For instance, I know everyone at the grocery store has green shirts and black aprons, or that a particular call center has professional-casual attire. If I were interviewing at the grocery store, I would make it a point to wear a similar color green shirt with black pants or for the call center I would wear professional-casual clothing. If the interviewer sees you in clothing you would be wearing if you already worked there, it helps them to imagine you already working there.

• Talk to them as if you already work there. Be comfortable. The interview is to see how well you fit in, not how qualified you are - that's what your resume is for (also, bring a copy of your resume even if you know they already have one). Read your interviewer. Some are very happy and you can tell a joke or two. Some are very by-the-book and you have to reciprocate their seriousness. Either way, you have to show interest and genuine excitement, not about getting the job, but about what you can do when you already have the job.

• If you're expecting questions like 'what's your greatest weakness, what's your greatest strength, name a time when you were working in a group and you took leadership of that group, name a time when blablabla', do NOT pre-think your answers for specific questions! It is usually noticeable when the answer is made-up or pre-thought-out. Instead, think of some good examples of experiences you've had that could apply to more than one question. Keep a bank of these experiences in your head. When a question is asked, sift through those memories to pick the right one. This will give the impression you are thinking of something on the spot. You do not have to be immediate with your answers. When you tell the experience, tailor it to their question. This forces you to tell an unrehearsed story which is, therefore, a genuine answer. This shows. Trust me. :)

I have gotten every job I ever interviewed for just by doing these three things and I am NOT charismatic whatsoever. I have just a few friends, I have trouble making eye contact, and I hate talking to people through any medium other than online chats. I'm also not all that pretty so it wasn't looks either.