Here’s the rule of three. It’s a long time computer-person rule of thumb that you can apply to your life now. It’s also called the Backup 3-2-1 rule.
3 copies of anything you care about – Two isn’t enough if it’s important.
2 different formats – Example: Dropbox+DVDs or Hard Drive+Memory Stick or CD+Crash Plan, or more
1 off-site backup – If the house burns down, how will you get your memories back?