HR is awful. They are the worst group of people I have ever encountered.
Don't expect extra hours than whatever you came in with.
They might just as easily take away hours you were told you'd have during the interview as they give you the job.
They are not very understanding about extenuating circumstances (i.e. make sure you provide documentation with each and every call-out).
Favorites are played.
You are trained by people that have literally only been there for months before you (so your work performance will definitely be subpar).
You will need to work with urine and stool if you are in the nighttime shift.
It's like high school, the work area; people are flirting, people are bullies, people are really, really mean.
No raises.
Will ask you to come in early/work extra the day of or a few hours beforehand and if you can't make it, they will hold it against you.
They might terminate you just because they can't afford you to hold a position, and they'll make up some random excuse.