There are a number of backup options out there. Check online. Here's a rough guide if you want to do it manually.
Get either a thumb drive or external hard drive that is at least as large as the storage capacity of your machine. Copy your personal folder (should have your name or username on it) to that drive. This folder should contain most of your important files (docs, pics, music, etc.) Do the same for all other users of your machine. If you have saved any files to other places not in your personal folder copy these as well.
Two things -- you can back your files up to the cloud if you have enough storage, but if you have never backed up your machine before, this could take a very long time. Also, this will not save copies of any installed software. You will need to reinstall after you acquire a new machine.
And finally, stay close to your Surface in case it decides to self-incinerate while you're doing the backup.
This is probably not 100% complete, but it will get you most of the way there.
Good luck.