Study like crazy! If you get stressed out enough, your period won't even come. At least, that's how it works for me. Stress totally postpones my periods.
Otherwise, I wouldn't tell your professors- that's just...weird.
Unless, of course, you're on a personal level with your profs. Just take some Midol, soak in a hot bath at least once a day for cramps, and get someone to give you back rubs!
And make sure you have tons of supplies with ya! Everyone knows what a drag it is to be taking a test and realise you forgot to restock the tampons in your backpack/purse.