This is a city that is very busy and crowded with tourists.

Pickpockets exist in every city. They are more numerous in cities with many famous tourist icons. You may see them around major tourist attractions and on buses, trams and metro. You should also know that pickpockets come in all shapes and sizes, a young child may seem harmless, but can be very cunning.  Some tourists do silly things and ignore or forget all the good advice they have ever read about or been told about.  Just beware of your surroundings and use a security wallet, particularly if you are a novice or inexperienced traveller. You wear it under your clothes and carry your passport, credit cards, airline ticket and some cash in euros. Or, as an even safer alternative, leave most of your cash and all but one credit card in the safe in your hotel. Carrying a pocketbook or wearing a "belly bag" (or "fanny pack"), or an unsecured backback, is an invitation to potentially become a victim. Women who can bring themselves to carry their "necessities" in a multi-zippered pocketed jacket instead of a pocketbook are wise travelers. If you must carry a purse or travel bag with you, there are some cross-body bags that also have a wire mesh throughout the body of the bag. This will prevent your bag from being slashed and your valuables stolen. 

Always carry the full address for the hotel that you are staying at. You may forget the exact street, and it may be handy to show the paper with the address to a taxi driver.

Wear comfortable, broken-in shoes as you will need to walk a lot on cobblestone paved streets and on sidewalks with uneven pavement. Wearing heels in Rome, or fip-flops, is not practical. A sprained ankle is not a souvenir you want to take home from your trip.

Do some pre-tour research and make a list of your top five "must sees," then check their opening hours and locations and plan out an itinterary. The list will depend on your length of stay in Rome. It is best to only see one "major" attraction per day, and save the rest of the day for free attractions like piazzas, churches, and fountains, and for walking through neighborhoods at your own pace, stopping for the occasional drink or gelato, of course! In addition, some special tours, like the Vatican "Scavi" tour or the Colosseum Underground and Third Tier tour, sell out, so you will want to book in advance. And, the last thing you want to do when on your vacation is stand in long lines in the hot sun. So, pre-purchasing the "skip the line" tickets from the official websites for the Vatican Museums and the Colosseum complex (combination ticket with the Roman Forum and Palatine Hill) is highly recommended (also note those official websites offer the most reasonably-priced tours).

A way for an introduction to Rome is to take a two-hour orientation tour on one of the hop on/hop off double decker tourist buses.  You can do a complete trip the first time round so as to get an excellent overview of the city, and some companies have a reduced fare for just doing the one-time loop. Do be aware that the hop on/hop off buses are not the best way to see all the sights as they cannot get to many attractions in the historic center -- instead, the best way to see many of Rome's sights is by walking!

The public buses and the metro are a great way to get around the city. You can get a day or a multi-day travel pass if you will do a lot of traveling by public transportation. A 7-day travel pass in Rome is an excellent investment --the pass will pay for itself after only 3 days of frequent travel on the bus, tram and metro systems.  

Alternatively, the Roma Pass will give you 3 days of travel about the city on the metro and buses, free admission to your first two sites and discounted admission to certain other attractions. Note that you still need to call the Galleria Borghese to book a timed entry ticket - you can call from the USA, then use your Roma Pass for entrance.

Also note that the Vatican Museums are not included in the Roma Pass. Bus 40 and Bus 64 from the bus plaza in front of the Termini station both use a similar route to St. Peter's Square and return. These are two of Rome's public buses that are dedicated to the "Vatican Shuttle Route".

Don't be afraid to take taxis. Usually it is best to find a taxi stand (so you know they will be a licensed, official taxi), or you can have your hotel or restaurant call a taxi for you. Since your time in Rome will always be limited, dealing with an unknown and confusing bus and metro system may be more costly in time (and therefore money) than taxis, which are relatively reasonable, particularly with 2 or 3 people traveling together.