What's it like working at a fast food joint? What should I expect and how can I prepare myself?

you are probably required to do things as instructed, you are not given the choice of figuring it out for yourself

If you are "thin skinned", grow a thicker one. Between grouchy customers and grumpy bosses, it's not fun. But as the other user said, it's a way to get stuff. Good luck.

I worked at Wendy's in high school. It was my first job. I got it the day after I turned 16. It sucked. It so, so, so, so, so sucked. It was grueling work--hot, exhausting, and thankless. I watched the clock every minute I was there. I have burn scars on my forearm from reaching into the potato oven that are still there years later. But I was able to buy a car and buy myself the kind of clothes my folks were too broke from having so many kids to buy me. So, yeah, it was worth it.

Go sit in one and pay attention while eating a meal.

You can expect a lot of hasty instructions, and a lot of hard word.

Prepare yourself by accepting the fact that you will be following orders that may make no sense