If you believe you are being followed and you want to erase all the data you have on your computer, consider the following advice: Do not only use the delete function on your computer; it cancels just the reference but actual documents may still be stored on your hard disc and can easily be restored by a third party. This technique is the same for flash drives, like those used in digital cameras. By all means, overwrite your data. It is recommended to use tools like ‘Eraser’, ‘Secure Eraser’ (both Windows) or ‘Super Eraser’ (Mac). These programs use different matrix to overwrite the file with various numbers that make it impossible to restore the original file.
Furthermore, it is highly recommended to regularly wipe and to reinstall any software on your devices (at least twice a year). Make sure that you do not just format your hard drive, but that you overwrite the data for the same reason as you overwrite your files. You can use the recommended tools for this process as well.