Sheer misery! Cramps, soreness all over, a general icky feeling, tired, irritable, clumsy, forgetful...could be anything cuz it can be different for each girl. Maybe you'll get lucky & it won't be so bad.
Have you ever had your period before? If you have then within 30 days you will have it again unless you are pregnant or have some other health issue. If you haven't had it before then a lot of it depends on genetics, ask your mom when she first got hers and that will give you a rough idea.