Sadly the old adage ‘don’t judge a book by its cover’ never seems to apply to people. Within the first ten to twenty seconds of meeting someone new, most people have formed an opinion of you based entirely on what you look like. Right or wrong, they are judging your clothing, hair style or cut, makeup, jewelry and shoes. In some instances they are also judging perfume/smell, eyeglasses, body piercings, tattoos, etc.
This makes it even more important to be dressed appropriately for an interview and for at least your first day at work (until you figure out what the company culture is with respect to clothing). The focus of an interview needs to be on your skills, what you have to offer the company, how your background is a fit for the opening and the company and NOT on what you look like.
In all the years I’ve been recruiting, I’ve near once heard someone say there was a problem with a candidate showing up wearing a suit. Even for a job where you will never wear one in the course of a normal work day, being dressed professionally for the interview is at the very least a sign of respect.
Once you are hired, you may find you are going to work in a t-shirt and pajama pants, but for the interview that sends a negative message.
If you have no idea how to dress professionally, I would suggest you Google it. There are thousands of sites with advice on what to wear. You can even ask the person scheduling the interview what is appropriate for their company.
In many cases I’ve been told to tell the candidate to wear business casual. A suit is not expected or required. That means you need to figure out what business casual actually looks like. Again, in some companies you could end up in pajama pants and a t-shirt, but for the most part you should lean towards something not quite that casual. Remember it is “business” casual not “lying around the house” casual.
To get you started, here are a few links offering advice on what to wear, how to dress for your body type, etc.: