The best practice to keep data safe is to keep it encrypted with at least AES Encryption Standard which is being officially used by US government to keep its data secure. You can use TrueCrypt, which is open source as well as freeware, for data encryption. Believe me, no body can decrypt properly encrypted data by TrueCrypt. The other practice is erase your data securely when not needed. O&O SafeErase is professionally designed to do secure data erase.
O&O SafeErase gives you complete protection against unauthorized access to any confidential data you delete! No matter whether it’s outdated financial information, e-mail archives, or personal files, you can be sure that with O&O SafeErase this data will remain permanently deleted. That’s because O&O SafeErase doesn’t just delete data – it annihilates it, using six recognized and recommended deletion methods, including ones practiced by the U. S. Departments of Defense (DoD), and the German Department of Security in Information Technology (BSI).