what type machine are you backing up? More than one?
you can get an ext HD that connects with cable or you can get one that is wireless. For a laptop or other computers around the house.
after that, how much do you want to back up, and how often? Most come with a progam that will run at specified times during the day (or night) backing up data.
I have ours at work run a backup three hours after the workday starts and again at the end of the day. All on its own.
Mikeeee