Hi,
DH and I stayed in Rome for 5 days ( Monday to Friday ) in June a couple of years ago. I bought a few guide books like the AA Rome spiralguide, which also have good maps in them, along with the Top 10 places recommended to visit.
I got a lot of help, advice and tips from people on the Trip Advisor Rome forum, which helped to save money and avoid queues at some sites.
I booked tickets for the Vatican Museum ( for the Sistine Chapel ) online which saved a HUGE queue. We spent a whole day there, as the museums and art galleries are vast, but I would say that the highlights were the fabulous ceiling paintings by Michaelangelo in the Sistine Chapel, and climbing to the top of St Peter's dome, for amazing views.
We bought dual tickets for the Forum and Colosseum at the Forum ticket booth, which we did first in the morning before it got too hot as very little shade, then crossed the road to the Colosseum where we bypassed a very long queue. Beware of scammers trying to sell you fake tickets.
The Trevi Fountain is also an absolute MUST, and worth seeing in daylight and also when lit up at night. It gets very busy, so go early morning if possible, to avoid the crowds. It is a popular place for just hanging out in the evenings, sitting on the steps.
Another must - see is the Pantheon, with its central hole in the domed roof. We also went to Castile St Angelo,and spent a morning there. This is quite near the Vatican.
You need to study a map of Rome, which is not a large city, so you can plan where to go and what to see on the way, so you don't waste time.
We had two evening meals on the piazza next to the Pantheon, and also on Piazza Navona, and Piazza Campo De Fiori, which was next to our lovely hotel.
It is best to stay somewhere central, so you can walk easily to see sights, rather than being at one end of Rome. Accommodation will depend on how much you wish to spend. I chose our hotel ( Hotel Campo De Fiori ) after reading very good reviews on TA. The rooftop terrace views are fab. You can watch the sunset over St Peters Dome in the distance.
You can read my review here.
www.tripadvisor.co.uk/ShowUserReviews-g187791-d208552-r33014124-Hotel_Campo_De_Fiori-Rome_Lazio.html