Job interviews are stressful! However, with the proper preparation, you'll feel more confident and go in with your best foot forward.
1. Do Your Research!
Make sure you read through the job description and are familiar with what you're interviewing for. I know- this sounds silly, but I've had candidates show up with no idea about what the job description even says. Make sure you know about the company as well- browse their website and get a general idea for what they do and what their values are. Many employers will want to feel like you want to work for them, not just any job you can get. While arguably not a fair expectation, it still pays to make sure that the employer feels you're invested in them.
2. Practice, Don't Script
Look up some common interview questions and go over what your answers are to them. Write down your accomplishments and think of examples of projects you did well or customers who you went above and beyond for. The key here is getting a general idea of what you want to say, but not memorizing a script- that can sound awkward in interviews and may be off-putting to the interviewer.
3. Dress the Part
Make sure you have clothes ready, ironed, and good to go the night prior. There is nothing more stressful than finding a run in your tights or your dryer breaking the morning of the interview and having to make a panicked run to pick up new clothes. As a rule of thumb, dress one step above the normal dress for the office- so for a business casual office, dress slightly more formally. For a casual office, business casual is typically fine.