First Job Interview + question

Besides the usual tips, anything important that people highly recommend? Last time I had a job interview was for a summer internship 4 years ago, which I got into.

Also, if I do get the job, I wanted to get people's ideas on when it is a good time to ask for vacation time. Should it be done during the interview or when is it generally a good time to? I already arranged something over a year ago for around july 4th, requiring me to take off thursday and friday prior. While I know people are given vacation time generally during a year, I think it would look bad since I would only be working for about a month and taking 2 days off. This is more nerve-wracking due to the fact that this is an entry-level job and imo I need to get as much experience as I can and I can't afford to take any time off. But I have no idea how these things really work so I'd like to get some advice from people who do have experience already.

Good time to ask for vacation is when the employer tells you that you have vacation time to take. Most employees do not get any vacation time for the first six months of employment. You have to decide between starting a career and your plans. It sucks. I know. I'll have to deal with that when it comes to my brother's wedding.

Do some in-depth research of the company.
Walk in confident.
Strut your stuff.
The company wants to invest in you. They believe that hiring you offers them greater ROI than not hiring you. So show them examples of how you've helped previous companies increase their ROI by having you there.