The same as Cleo does, I use
Time Machine too, but there must be something similar for PC/Windows users.
The advantage of using this kind of system is that you don't have to worry about backing up manually (or putting it off). Time Machine makes incremental backups every hour, every day, copying just the files that have changed since your last backup. It saves the hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for everything older than a month, and it does this all in the background, so you don't have to do anything. Well, aside from arranging to store copies of the backups off-site for real safety of course.