I have always heard that you should dress for the job you want. If it is at a company wear a suit, etc. I wore a nice pair of jeans and a nice top to my interview for a position at an independent grocery store and coffee shop. But the main thing is to just bring your personality. Be friendly and confident. Give them no chance but to hire you. The guy who hired me in that scenario was pretty laid back and a had a good sense of humor. He just wanted to find someone that fit in with the vibe of the place. And apparently my smiles and my commentary (I told him to hire me or else the other place that I applied to was going to get me first! Haha) won him over. I also had no prior experience. Just make sure to impress on them how reliable and hardworking you are.  

So I would go with the black pants, the flats, and the polo shirt. I am sure you will do great!  ;)b

Look at the interviewer with a friendly, open expression. Don't cross your arms or legs if you're sitting down because this gives a defensive message. Sit up straight but relaxed, hands palm-up on your knees. Look the interviewer in the eye when talking to them.

It can't hurt to show any work experience you have, particularly if it's in sales or whatever you'll be doing at the craft store.

is it a retail job?  I was in retail management for almost 15 years.  The things I looked for:
dress professionally, the black pants sound fine, be on time or a little early, come prepared, have a pen, answers to questions that sound positive but true.  Be confident, say you are a team player, smile.  Have someone role play with you and ask you questions.  You will do great!

come prepared, have a pen, answers to questions that sound positive but true. 

yes, and try and think of one question you can ask them about the company, the job, the team, something. You will almost always be asked in an interview if you have any questions, and it pays to have thought ahead and know you'll have at least something to ask.

Congrats on the job interview!

The black pants, polo and flats sound just right.  What you lack in work experience make up for in enthusiasm.  I would bring a resume.... outline the course you have taken.  You can list all the crafty things you've done and feel confident in doing.  Explain that you are in college and are looking forward to entering into the workforce to gain experience.

They will definitely ask you if you have any questions for them... 2 - 3 is normally good.  Such as: Do you offer any sewing/crafty classes here?  If yes, are employees encouraged to participate in them to learn more to better serve our customers?  You can ask about hours/days they are looking to fill (IE: part or full time)?  And.... you can ask; When will they be making a decision to fill the position and will they let you know one way or another?

If they ask you when you can start; be sure to say "immediately!".

Also, don't appear too high maintenance.  Yes, it's very important to look good, but don't do your hair up too much or wear a bunch of makeup, because it will make you seem shallow, which is something that companies are usually not interested in.

Is it too late to vote for the button-up shirt?  I dress a bit nicer than I would for the actual job when interviewing, but not too over-dressed.  I'm with everyone on the black pants and flats.

Michael's doesn't have sewing classes, but I think they have demonstrations.  You could ask if in-store demonstrations are provided by a vendor or if store employees are able to contribute to them.

I did interviews for a while at a major retailer.  It sounds like you are on the right track.  I can't tell you how many people showed up in gym shorts, a tank top, and flip flops.  It is not professional to show the interviewer your undergarments!  Lol.  The advise that others have given is good.  I will add a few things that are a bit different for applying for a retail job with a big company.  

1.  The resume is a good idea, but don't be too forceful with it.  We were required to give all applicants identical interviews (company afraid of lawsuits) and weren't allowed to use a resume as hiring criteria.  We weren't even allowed to read them.  They were just stuck in the applicant's file.    It wasn't always that way, but it is now.  They even give us the questions to ask.  

2.  Have a few good references from teaches, coaches, instructors, etc. that are not family members, even if you've never had a job before.  

3.  I know that every career guide recommends followup phone calls, letters, and visits.  Maybe one is okay.  Anything more than that is obnoxious.  We were required to interview so many people before we could fill a position.  The annoying people where put into the do-not-hire pile.  Irritating, demanding applicants make irritating, demanding employees.  

4.  Do not volunteer information that people can use to discriminate against you.  It is illegal for us to ask, but we can use some of this information against you if you bring it up.  These things include transportation, health, childcare, religion, political opinions, and maybe even veganism.  

5.  Realize that some major corporations are so scared of lawsuits that they are limited with the information that they can provide you.  For a ridiculous example, we were not allowed to tell someone that we weren't going to hire them or even if they were unhirable.  We were just instructed to tell them that we didn't have a position right now that meets their qualifications and needs.  Sometimes these people would be very persistent and get added to the do-not-hire pile.  

6.  Lastly, be very open with what you are willing to do.  If the position you applied for is filled by someone else, is there something else you would be willing to do?  We weren't allowed to call people and ask if people were interested in other positions out of fear of lawsuits.  If I had a shift that was even 15 minutes different from what the applicant put on the application, I couldn't offer the position to them.  

I don't know about that corporation, but as you can see many of the rules are based on the fear of lawsuits.  It silly, but if I do something for Bobby who is purple and not Mark who is green, well there's a lawsuit waiting to happen.  Silly, yes.  That's just the way it is.  Sorry that this is so long, but hopefully it is helpful.