Unlike France or UK, in Italy whenever you ask for water in restaurant or cafe, you will be brought bottled water that can cost you anything from €2.5 to €5. Some restaurants may serve tap water if you ask for it but mostly offer only bottled one. It's cheaper to buy water in bulk from a supermarket and carry it with you instead of buying it in restaurants or from vending machines. For instance, we paid €5 for 1.5 litres of water that costs 50 cents in the supermarket.
Most serving staff in cafes and small restaurants barely understands any English so it's better to learn some basic phrases and key words for ease of communication.
Plus all information is not shared upfront. Clarify all doubts before buying a ticket or ordering a meal.
Express train from Airport to Rome Termini costs €14 per ticket and a cab to city centre costs €50. Take a call based on how many of you are travelling together. As you exit the gates at airport, you will also find shared cabs, you can negotiate the asking rate of €20 per head down to €15.
Within Rome, single use metro ticket costs €1.5 and a 6 day multiuse pass is €24. Buy the latter if you know you will be needing metro often.
To know timings of key attractions to better plan your days use the website www.visitacity.com. It has a wealth of information.
Try to buy tickets online as much as you can to avoid long ticketing queues. Even if you take guided tours, admission ticket is still needed.
Also note that there is access to top to almost all bell towers and leaning tower of Pisa but unlike Eiffel there is no elevator till the top (Cupola at St. Peter's Basilica offers one till about half of the way) Climbing these towers means climbing 300-550 steps. So buy the tickets only if you are sure you will use them. One of us couldn't climb the leaning tower and those €18 were wasted for him.
Carry some cash on you as gelatarias and cabbies don't accept credit card. But leave your passport in hotel safe as you won't need it. Carry your country's driver's license instead as an ID.
Wifi is not a very common facility in public places or restaurants so if you need data access, buy a SIM card from Lyca mobile.
Avoid road side vendors as they don't care about repeat business - they simply fleece unsuspecting tourists. A road side vendor charged me €4 for a scoop of lousy gelato claiming it was medium in size when I had specifically asked for small.