Follow the 3-2-1 rule for your important data, ideally 4-3-2 or better. Remember, if you only have one copy of your data, you actually have zero copies of your data.
3 separate backups on
2 different media (ie 2 backups on 2 separate HDDs plus one on DVDs) with
At least 1 offsite (ie a satellite office or your parents house for personal stuff)