STEP 1
Head to the directory where the bank file is stored
Windows location
Spoiler : Path :
Mac location
Spoiler : Path :
Mac Users
In Mac OS X 10.7 and above(Lion), the Library folder is hidden by default. To show it, copy and paste "chflags nohidden ~/Library/" into the terminal app and press enter. It should now appear in your User folder next to documents, downloads, etc folder. To hide it again use "chflags hidden ~/Library"
STEP 2
In your folder named with your handle, you should see a "Banks" folder. Copy that "Banks" folder into wherever you think would be safe or convenient for you, such as;
- Cloud Storage services (Dropbox, Google Drive, Microsoft OneDrive, etc)
- A flash drive/External HDD
- Another computer/laptop
Pro-Tip
You can use software such as "Everyday Auto Backup"(suggested by Sureiya) to automatically copy the banks folder at set intervals of time to another location.
STEP 3
To put the banks data back into your StarCraft II installation, go to the same directory from step 1 and replace the banks folder there with your backup. As a general rule, you should delete the bank folder THEN move the backup in. If you merge the folders there may be problems.
This guide was written by @Mugy I just gave it it's own thread.