I would definitely suggest buying a small book on Rome because it really is a completely different experience when, apart from the visual treat, you actually know what you are seeing. There is so much history in every little stone found in this city that... it just makes more sense to be at least a little bit informed.
Second, if time is limited, as it usually is, then a rough plan is needed. Setting the "priorities", the must see places. For some it might be tossing a coin in Fontana di Trevi, for others seeing the Vatican Museum, and then for others eating a pizza.
Take your time and enjoy EVERY STEP you make there!
Ok, now, before you start the 'leg-torture' kick it off with an Italian breakfast - at any bar order a nice cup of capuccino and corneto (tasty pastry). The cafes on Piazza di S. Eustachio are the right place for this.
Ok... you're ready now!

