Amsterdam is famous for its canals, so taking a boat tour through the canal is obviously a great way to see the old centre.
The typical canal boat in Amsterdam is a flat glass-top boat. Flat, so that it fits under the bridges, and glass, so that you have a free view all around.
There are several companies in Amsterdam that offer boat tours, and you can simply go to one of the mooring places (see list on this page).
Canal tour boat (company Lovers)