I agree to suit up if you can- the more professional looking the better- you are there to impress and sell yourself! Nice slacks, nice shirt, and blazer or jacket with closed toed shoes is perfect.
Light makeup- you want a day face- you want to look clean so for me I just do my bare minerals makeup, a neutral eye shadow, and some mascara. I don't do lip gloss but chapstick if I feel I need it.
For hair- don't do a bun it's too harsh but you want your hair pulled away from your face. I usually do half up half down. I clip it back also so it's loose overall but still off my face.
Interview questions- google "interview questions" and pick the ones you think might be asked. Practice OUT LOUD until you sound natural.
I used to interview people and one question that I often would ask is "tell me about yourself." I wanted to hear things like "I'm a hard working person, this is where I went to school, this is where I have worked, this is my goal, etc." DON'T TELL your life story- just a few things about yourself and what you have done so far.
Thinking about your answer before you say it. Take it in, take a breath, respond. This also avoids a lot of "uh uh uh."
And don't ramble! The worst was when I knew someone was unprepared and they'd go on and on about stuff and I was like dude just give me a one to two sentence answer.
SMILE! Thank them afterwards for their time and tell them you hope you hear from them soon. You can get a person's vibe from the interview also- if they are more relaxed a chuckle here and there is fine.
If you get nervous remember to just take a deep breath and slow down. Usually people are slightly nervous at first, that's okay, after a few minutes things are usually fine
Seriously there is a ton of information online about interview etiquette and so on- take advantage of it!
And whatever you do never say anything bad about ANYONE. I can't tell you how many people would talk so much crap about their current bosses or last bosses and I'd be sitting there like really? Yeah you are so not getting hired here! lol.