Do I have to make a portfolio or something to show prospective employers? Anyone know anything about this? If you were going to hire someone what would you look for?

I would definitely have a portfolio. For me that is the first thing that I would look for. Of course speed is another biggie. I went on an interview a couple of years ago and they asked for pictures and they wanted me to decorate a cake on the spot. it was for a grocery store so they weren't looking for an advanced decorator. They wanted someone that could ice a cake, put some roses on it and be able to airbrush and put on a kit. And of course because the are a production bakery they wanted you to be pretty fast.

Definitely a portfolio and a resume that outlines your work in the industry and education. I worked at a bakery (not as a decorator then)...when they were looking for a decorator/baker. They wanted to see pictures mostly...not only to see the work ,but to gauge the variety of styles because all bakeries want different things and you would have to be trainable. A huge concern is how fast you are. No doubt someone will ask you to crumb coat, stack and decorate a cake with specifics like roses or whatever. I'd say it depends on the bakery as to what type of cake they primarily produce...custom shops would lean more toward custom design and fondant use whereas your larger commercial operations want the consistent look of a pre-designed cake in their portfolios.
Good luck in your search!

When I interviewed for my first job in a pastry kitchen, I submitted a resume along with severalpictures of cakes I had done. They called me back in for a second "practice" interview. I had to show my icing skills, do basket weaves and pipe borders. Be prepared!