My laptop keeps saying I am almost out of backup storage, what do I do?
By backup storage do you mean space on your hard drive or space on a cloud hosted site that you back your files onto? If it's the former, then you should invest in an external hard drive and back your files up accordingly and clean out what you have on the drive in your laptop. If it's the latter then you probably just need to buy more storage space. Although, if you happen to be using a service like dropbox, you can get free storage from things like friend referrals and following them on facebook/twitter.
I'd actually recommend that you forgo the external HD as a backup solution. There are plenty of free or cheap cloud hosted services out there. Let someone else's sturdy infrastructure store your documents.
Chris recommends a good one -- Dropbox. If you have a bunch of images that you want stored, you can also use Flickr which will give you 1 TB of free storage. The great thing about the hosted solution is that you have access to these documents very easily through their website or apps. Unlike a external HD, which you would then have to carry with you, find a plug, and hear it whirring in the background.