You may be the free spirited, "wing-it" type, but you're not going to feel so free-spirited when you've just been sent out of your fourth overcrowded hotel without a room at 3 a.m. Unless you don't mind setting up camp somewhere along the side of the road or driving through the night with drooping eyelids, make hotel reservations before you leave.
The same last-minute travel Web sites that can point you to airfare and rental car deals will help you book last-minute hotel rooms, often at a dramatic discount. As long as you have a general idea of which town you'll be stopping in each night, you can feel secure in the knowledge that you'll have a place to rest your travel-weary head.
You might also want to make restaurant reservations, especially if you plan to visit a touristy restaurant (which includes any restaurant that's been featured on a reality TV show) or you're visiting at peak season. Many attractions, like the Statue of Liberty ferry, also require reservations. You could actually be turned away if the place is full and you haven't booked your ticket in advance.