If you sign up for a free 30-day trial that requires your credit card number up front, MAKE A NOTE of what day you signed up. Especially if you don't actually want the service past the trial.
If you are dumb like me and get charged lots of money because you didn't pay attention, it never hurts to ask nicely for your money back even if their policy is VERY VERY CLEAR on their website where it says "After the 30-day trial period, absolutely no refunds will be given." Sometimes nice people named Randall give your money back anyway.
But really, you should just make a note the first time around.
