Pizzeria Da Baffetto on the Via del Governo Vecchio, off the bottom corner of Piazza Navona is fantastic.
Looks really uninspiring, Formica tables and grumpy waiters but the queue round the block should give you a clue. Get there early (we queued for an hour and a half last time) and the Pizzas are amazing.
Obviously if you don’t like pizza then avoid it.
The bus tour will drop you off handily near all the most obvious sights. If you are doing the Vatican then see St Peter’s Basilica rather than the Vatican museum itself. They will try and lure you in with promises of The Sistine Chapel, but you could grow a beard in the queue it’s that long, and the chapel itself is heaving with people, many of whom were loud, kind of obnoxious and a bit shovey. Not the ideal venue for appreciating Michelangelo’s mastery if you have even the teensiest bit of misanthropy.
If it is raining then the Pantheon is cool. I spent far too long watching rain pour in through the demon’s hole (stop laughing) and into the rain catchers in the floor. I enjoyed that more than the low walls and broken pillars my DH is bloody obsessed with. The horses who pull the carriages that wait outside the Pantheon are lovely and friendly too.
I genuinely loved the Trevi Fountain, and the wickedly strong espresso I had in an underground cafe just opposite it.
Wear comfortable shoes, and try to avoid bringing a Roman History obsessive who wants to spend the entire time in the Forum, that’s my best advice on Rome. 