I think one of the major differences between what we do and what was done in the past - we don't dig - is driven by the fact that we don't have to - in the past, there were no archaeologists, thus, if you wanted to find out about a site, you had to get your spade out.
One key aspect of what we do, is the free sharing of information - many of us regularly uncover new sites, or find new research that sheds light on existing sites. Our prime objective tends to be to share this with as many people as possible in as accessible a format as possible - which is where the Internet comes in.
This differs from many archaeologists who are more concerned with peer review than public digestion. Often, public presentations are only made where they are a requirement of the funding.
We are also a great deal more eclectic - whilst I tend to agree with FW about guessing what the ancients were up to, it is notable that few archaeologists analyse placenames, relationships with other sites, landscape features, local legends, writings of antiquarians etc, when it comes to discussing a particular site. This is partly to do with the very fact that we are not archaeologists - we do not get bogged down with the detail of a dig and therefore have plenty of time to look much further afield for information. It also has to do with having a more top down approach - the fact that an immense amount of information can be gathered about a site without the need to dig it up. I often think that this should be the driver behind modern archaeological research, which often has been reduced to the level of - which site is going to be destroyed next, or, which site would be most interesting/rewarding to dig.