A Traveler in Rome by H.V.Morton by skywalkerbeth
You simply must buy this book before or after your trip. It is the most enjoyable read and there is not one superfluous sentence in its entire 400+ pages. The author has such a breadth and depth of knowledge, I was even fascinated wondering how he must have crafted the book!
I know this doesn't match the title of the tip, but VT doesn't give a category for general tips about preparation, etc. I may end up moving this!