Steam keeps your games updated automatically as long as you are connected to the Internet. If you are using a pirated version, then you will have to fend for yourself. :P
If you do not have a broadband Internet connection, then you would have to find someone who does who is willing to let you either use their broadband Internet connection or install the game on their computer and then use Steam's backup feature to create a backup of the game files that you can then restore onto your own computer from a flash drive.
Providing that the computer to which you restore on actually has a steam account with a purchased version of that game on it. Otherwise the files will be there but the game will be unplayable.