If you've got some important data - say like, data you've accumulated over 2-3 years that's irreplaceable - we suggest you grab an external or sign up for a cloud backup service today. You don't want to end up like this university researcher who's potentially lost years worth of data that may have led to a possible cure for prostate cancer. So, if you haven't backed up in ages and have some really important stuff on that laptop of yours, we've provided two stupidly easy ways to get your stuff backed up ASAP.
External Hard Drive: By far the easiest way to back up your data is to grab a big fat 1-2TB drive and moving all of your stuff onto there. If you've got a Mac, use Time Machine to get some version control of your files. It's best to set the back up schedule for at least once a month.
The Cloud Service: Also a ridiculously easy way to get your stuff up - simply install the software, pay the $5 monthly fee, and sleep safely knowing that your data's going to servers that are protected by militarized forces... okay, maybe not that last part, but it's good a good idea to have your data stuffed somewhere far away from your laptop. You know, just in case the would-be thief decides to take your backup drive as well along with it.