I’m in Italy now, and was in Rome the previous 2 weeks. For transportation, go to any Tabacci (tobacco/cigarettes/transportation pass store), and buy a transportation pass for 2 days. It’ll be good on all metro (underground/subway) rides and bus rides over those 2 days. Be sure to stick it in the validation machine on just your first bus ride, and at the entry turnstile at every metro station you enter. Keep it safe, as you’ll need it.
Termini station has a metro stop, but there’s also a convenient taxi stand, where you can easily catch a taxi. Rick Steves’ guidebook (either paperback or downloaded online) mentions that he takes more taxis in Rome than in any other city. They’re very convenient, pretty honest (still, make sure they are using the meter, which will very likely be the case without any concern), and rides are usually never more than €5 to €12 anywhere in the city. For buses, I found GoogleMaps app to be invaluable this trip … it tells you the bus number (or numbers for more than one bus) to get you from your originating location to your destination, where to find the bus stop, and how many stops until you get to your destination. If you’re using GoogleMaps with a smartphone, it’s a snap.
Ghetto in late afternoon/early evening was fantastic on 2 separate evenings.
If you don’t have reservations already, and want to dine at a particular restaurant, show up at 7:00pm (or whenever it opens), and you might get a table.
Hop On Hop Off, skip those, and do it on your own. For upwards of $300, a private guide would get you an even better visit, but for the price.
Vatican Museums were absolutely packed. Lots of groups, many clearly with official Vatican Museums guides, booked through the official Website. We used a private guide (see Rick’s guidebook for recommendations). Whether you get a guided tour there, or do it on your own, or get one of the special options that the Vatican Museums offer, book your admission ticket directly through the official https://m.museivaticani.va/content/museivaticani-mobile/en/organizza-visita/tariffe-e-biglietti.html website, not a separate tour company. And book your tickets as soon as they go for sale - monitor the website regularly to find out when they’re for sale. When your date comes up for sale, entry times and tickets call sell out very quickly. Tickets for later in the day (and tours in languages other than English) can often still get you in the door, even if the before noon entries, or the English guided tours for the day are already sold out.