When it comes to genealogy, people are often interested in finding out how far back in time they could theoretically trace their ancestors if all of them had some sort of written chronology (just theoretically speaking, of course, as written documents only came up “recently”). So how far back could one go in Italy? Who were the first people to actually live in Italy? Nobody can give you a 100% exact answer to that, but it is known that people lived in Italy as far back as 200,000 years ago. However, those were not the same kind of people we know today, there were a different species even – called Homo Erectus. The modern people, the Homo Sapiens Sapiens only turned up in Italy about 12,000 years ago. Scientists who did genetic tests on remains of those people found out that those people originally came from West Asia.
Some time around 5,000 BC, i.e. about seven thousand years ago, people from Greece came over to Italy in their boats. These people, of course, brought knowledge, tools, and even animals with them. Over time, they spread North and populated more and more of the country. More information about what happened in more recent times in Italy can be found in Italian History 101.
So basically, if you know that you have some sort of Italian heritage, you can assume that your very early ancestors were either from Western Asia or Greece. That is quite an impressive heritage – unfortunately you will never be able to trace your heritage back that far. People who are lucky enough to be born into a family that has good documentations over the centuries (e.g. in official registers) might be able to trace their family back into the Middle Ages, but not very much further as official, written documentations, like birth, marriage, death, did not start until the Middle Ages, and even then not everybody was accounted for. For a long time it was only people of a certain “worth” that were documented.
People with an Italian surname in the USA will often have an interest in tracing back their family's history. First, you will have to find out when your ancestors did come to the USA – which can be fairly easy if it was your parents, grandparents or your grandparents' parents who were the immigrants.
Basically, Italians were not such a big group of immigrants until fairly recently, i.e. 1861. So you have good chances of actually being able to trace that back. With the help of the internet (and maybe with the help of your family's documents if there are any), you can then start working on tracing your actual Italian ancestors from long ago. It can be a very time-consuming process, but the results can also be very rewarding. These days, you also have the option to pay a professional to trace back your family tree for you.
Italians have a few traditional guidelines when it comes to naming their children – this can help, but can also be confusing if you find plenty of people with the same first name and even the same surname. The general naming rules for Italian children are that the first son is named after father's father. The first daughter is named after the father's mother. The second son is named after his mother's father, and the second daughter is named after her mother's mother. If there ever was a third son or daughter, then other names from other family members were chosen.
Imagine two sisters. Both of them have their second son in the same year. So they end up having boys of the same age with the same first name – but they will have a different family name. If you find such a cluster of similar first names but with different surnames repeatedly in the same geographical region, then you can assume that there must have been some common ancestor. But of course it can also all become quite confusing and many different factors have to be taken into account.
Like most other countries, the Italian used surnames to be able to keep people apart. There are family names that describes someone's relation (e.g. di Pablo – son/daugther of Pablo), their profession (e.g. Contadino – the farmer), their original home (e.g. Romano – from Rome), or someone's physical appearance (e.g. Basso for a short person).