The easiest way to do this is to set up automated backups with backup software that permits flexible scheduling and automatic execution, so your backups can occur completely unattended. Don't just limit your backup to selected files, either. Keep multiple copies of your data for additional insurance, and always keep at least one copy off site in case of theft, fire or other disasters. An old copy is better than no copy at all. You'll find that, should disaster strike, your entire hard drive can be restored in a matter of minutes to a few hours.
Tape continues to be the best value for backup media.
Choose a tape driver and tape capacity which can back up your largest hard drive overnight without changing tapes. Rotate your tapes, regularly retiring old media and introducing new media. Re-using the same tapes and having all your backups on one media set spells trouble, and leaves you highly vulnerable. The more storage sets you have, the less data you'll lose. Start a good habit now and begin backing up routinely.