Many travel sites charge a commission for reservations, so the hotel raises the price to cover the commission. Consider the people traveling with you. Traveling with people who are happy and well rested is always more fun than those who are grumpy and tired. Get a map. Don't assume that you will be able to just feel your way through the city.
Many cities have confusing signs and one way streets.
If you are going to be late, call ahead. A quick phone call from home, or a pay phone off the the highway, could save you from spending the night in your car. Many hotels offer night boxes or will wait up for you, if you call ahead. Spending a few minutes researching can often reveal those hidden rates.